KABUL - Seven Afghan security personnel were killed in a mis-targeted NATO air strike in the remote northwest of the country, the defense ministry said Saturday.

The "friendly fire" incident occurred when NATO and Afghan forces searching for two missing American paratroopers in the barren, rugged area clashed with the Taliban.

"Due to a NATO forces air strike on November 6 in Badghis province, seven Afghan security personnel (both army and national police) were martyred and also some were wounded," the ministry said in a statement.

NATO's International Security Assistance Force (ISAF) said that more than 25 ISAF and Afghan security personnel were killed or wounded during the joint operation.

It said it was investigating whether some of those casualties resulted from friendly fire. However, one Western military official, speaking on condition of anonymity, confirmed to AFP that it appeared to be a "blue-on-blue incident" -- a military term for friendly fire -- with "a huge number of casualties".

Afghan defense ministry spokesman Mohammad Zahir Azimi told AFP there was no doubt Afghan personnel had been killed and injured by their international partners.

"It was an erroneous air strike which caused casualties to friendly forces," he said.

More than 100,000 troops under NATO and US command are in Afghanistan fighting a Taliban insurgency now at its deadliest in the eight years since US-led troops toppled the Islamist regime.

US President Barack Obama is considering a request from military commanders to boost troop numbers by up to 40,000, a decision not likely to be made public for a number of weeks.

UN chief Ban Ki-moon said about 200 UN expatriate staff would be temporarily relocated outside Afghanistan after an attack on a guesthouse on October 28, which killed five UN workers.