MANILA, Philippines -- The Armed Forces of the Philippines (AFP) has launched offensives against the Moro Islamic Liberation Front (MILF) rebels in a string of attacks in Mindanao, the Chief of Staff, General Alexander Yano said Monday, as he branded the MILF assault as a “virtual declaration of war.”

Yano said the rebels "entered" the town center of Kolambugan and outlying villages in four other towns -- Kauswagan, Maigo, Linamon, and Iligan City. Fighting between government and rebels troops in the area is "intense," he said.

The attacks came a day after the rebels ambushed an Army convoy in Mulondo town, Lanao del Sur province, leaving seven soldiers killed and 12 others wounded, and a week after military offensives dislodged 500 rebels from North Cotabato province.

Chief Inspector Jamira Estrada, spokesman of the PNP in Northern Mindanao, said the guerillas, under one Commander Bravo, were now occupying the town hall of Kolambugan, including the town police office.

Estrada said a Catholic priest, Father Reggie Quijano and few parishioners stayed inside the church in Kolambugan town center.

"They were not taken hostage, they remained unharmed but could not leave the place," Estrada said in a radio interview, contradicting reports by other military officials that the MILF rebels took hostages.

Brigadier General Hilario Atendido, chief of counter-terrorism unit Task Force Tabak, said earlier in the day that Moro rebels held civilians hostage and used them as human shields to repel military offensives.

"That is why we cannot enter the area. They [MILF] are using the civilians as human shields," Atendido said in a phone interview.

Moro rebels who attacked Kauswagan town, but failed to occupy it, also took civilians as hostages as they retreated, Atendido said.

"We will go after them," Atendido said, adding that the rebels were concentrated in Kolambugan.

Outnumbered, the policemen in Kolambugan decided to withdraw toward adjacent Linamon town.

Portions of Iligan City and the Zamboanga highway had been closed as clearing operations launched by the 4th Infantry Division were ongoing.

Agence France-Presse, quoting residents, reported that at least 16 civilians were found dead in the affected towns in Lanao del Norte.

Nine bodies were lying bloodied by a roadside in the village of Lapayan in Kauswagan as black smoke billowed from houses burning in the background, they said.

Five other civilians were killed in another village by the marauding MILF rebels, residents fleeing the area told AFP.

Many other civilians were wounded as they tried to catch the last vehicles leaving the area.

Another rebel unit struck the town of Maasim, leaving two civilians dead as they ransacked a pawnshop and looted a drug store for medicines.

"They killed two people," said military spokesman Major Randolph Cabangbang. "The rebels also shot a power transmission [facility] that caused a brownout."

Yano called the MILF atrocities, which include an ambush on an Army convoy, as a "virtual declaration of war" and could not allow the attacks to go on.

"The recent MILF perpetrated incidents in Mindanao is a virtual declaration of war against the duly constituted authority," Yano told a news conference in Camp Aguinaldo.

"The AFP shall not allow this to go on… We are now taking military action to stop these atrocities, these developments are clear manifestation of the insincerity to the peace process of a significant portion of the MILF," he said.

Asked if the military was also declaring war with the MILF, Yano did not give a categorical answer. "We are actually conducting an offensive operation now against the groups," he said.

Yano gave President Gloria Macapagal-Arroyo a briefing on the situation in Mindanao.

Yano could not immediately assess the scale of the fighting. He also could not confirm if there had been casualties.

"We just had a few hours into the fighting but let me just report to you that there is intense fighting in those local areas, it has not escalated into a widespread scale outside Lanao del Norte, but fighting is intense in those mentioned areas," he said.

Yano said there were "enough" forces in the province, but reinforcement could be called in "depending on the developing situation."

Army Chief Lieutenant General Victor Ibrado said some battalions have been alerted to augment the 32nd and 35th Infantry Battalions there.

Ibrado said air support would be called in when requested by ground commanders.

Provincial spokesman Lyndon Calica said the rebels had overrun and torched a police outpost and burnt combat vehicles, also taking an unknown number of civilian hostages, among them the owner of the town's main department store.

"Kolambugan is practically under the control of the MILF," Calica said.

Earlier in the day, a Rural Bus transit with body No. 1567 driven by Antonio Aurelia was ambushed by suspected MILF rebels in Barangay Kulasian, Maigo town, also in Lanao del Norte.

Speaking over the radio, bus driver Aurelia said he has about 18 passengers going to Iligan City from Zamboanga City.

As they reached Barangay Kulasian, he saw men in fatigue uniform conducting checkpoint.

"I thought they were military men manning the checkpoint so I stopped," the 40-year-old Aurelia said.

"But as the bus was about to stop, they started firing at us with automatic rifles as they chanted "patayin sila lahat [kill them all]."

Even before the bus came to a complete halt, firing started.

"They shot the bus with automatic rifles," Aurelia said. "I lost control of the steering wheel."

"I was the target so the bus could stop," he said. He said he and two companions, a passenger and his conductor, ran for their lives as the gunmen were chanting "kill them all."

Quoting a co-driver, Aurelia said many of the passengers on board his bus unit were seen dead inside the bus.

"My colleague sent me text messages saying they saw my bus with many dead," Aurelia said.

Meanwhile, Executive Secretary Eduardo Ermita said Defense Secretary Gilbert Teodoro has ordered the Armed Forces of the Philippines to conduct "clearing operations" in the towns of Kauswagan, Kolambugan, and Migo in Lanao del Norte.

"This is a problem that has to be dealt with whether or not there is a peace process," Ermita told reporters in an interview at the Ninoy Aquino International Airport Terminal 3 for the installation of the bust of Benigno "Ninoy" Aquino on his 25th death anniversary.

Ermita said the MILF leadership has vowed to account for the acts of their commanders on the ground through the ceasefire committees.

He said the joint coordinating committee on the cessation of hostilities, which had been tasked to monitor the ceasefire between the MILF and the government, would investigate the incidents.

Earlier in the day, the government said it would take “appropriate steps” to deal with the situation in Mindanao.

Ghazali Jaafar, MILF vice chair for political affairs, said the offensive in Lanao del Norte had no "clear orders" from the MILF leadership.

"They acted on their own and we are doing our best to pacify him and restore normalcy," Jaafar said of the attacks.

He said Commander Bravo has no direct orders from MILF hierarchy and he acted on his own for reasons only known to him.

"We have sent emissary to inform him his action was in violation of the ceasefire agreement," Jaafar said, adding that the MILF also wanted to find out what triggered the attack.

"Commander Bravo would not launch attacks unless he is provoked," Jaafar said.

The 12,000-strong MILF has been fighting for an Islamic state in the south of the predominantly Christian Philippines since 1978. It signed a ceasefire agreement with Manila in 2003, paving the way for peace talks.

But the Supreme Court two weeks ago aborted a deal with the government that would have given the rebels control over vast areas in the south.

Shortly after, the rebels attacked government positions and took over more than 20 villages in another southern province. They were eventually pushed back but the retreating rebels looted and burned many houses.