MOGADISHU ? Somali pirates said Tuesday they had hijacked a small sailing yacht with two foreigners on board, most likely a British couple reported missing since leaving the Seychelles last week.

The hijacked yacht was heading back to the pirate lair of Harardhere in central Somalia but the pirates who spoke to AFP from there could not formally identify the two hostages.

"We don't know their nationality yet but I can tell you that we have a small boat with two people on board. They are coming to Harardhere, and only then can we start negotiating," Abdi Yare said.

"This was an unexpected catch because nobody could have predicted that two people on their own would have dared to venture out in the Indian Ocean at this time," said Yare, speaking by phone from Harardhere.

Another local pirate leader who refused to be named explained that the yacht was attacked by two pirate skiffs.

"Thirteen pirates on two speed boats snatched this small boat very far from the Somali coast," he said, without specifying the exact date of the hijacking.

The British foreign ministry earlier said it was urgently trying to locate a British couple whose yacht sent a distress signal while sailing near pirate-infested waters, and has not been seen since.

Paul Chandler, 58, and his wife Rachel, 55, were heading from the Seychelles towards Tanzania in their 38-foot (11.6-metre) yacht the Lynn Rival when their emergency beacon went off on Friday.

"We're in touch with the family in the UK and the Seychelles coastguard, which continues to monitor the situation and has conducted a search of the area," a spokeswoman told AFP.

Britain's Maritime and Coastguard Agency said an Emergency Position Indicating Radio Beacon (EPIRB) was activated at 2200 GMT Friday.

"They had left the Seychelles on October 22 and were going on a 150 nautical-mile passage southwest to the Amirante Islands, en route to Tanzania," the spokeswoman said.

In a statement to AFP on Tuesday, the coastguard in Seychelles did not rule out a pirate attack, confirming that a search was underway for the sailboat.

"We are monitoring the situation and at the present moment there is no confirmation that the Lynn Rival has been taken by pirates, even if the probability of hijacking is high," said coastguard commanding officer Lieutenant Colonel Michael Rosette.

On Wednesday the Chandlers said they were running in a replacement outboard motor, completing departure formalities and expected to leave the Seychelles the next day.

"We probably won't have satellite phone coverage until we're fairly close to the African coast, so we may be out of touch for some time," they wrote.

The hijacking of the yacht brings to eight the number of boats currently in pirate hands, together with more than 150 crew.

Since last year a flotilla of foreign warships has been patrolling the piracy-plagued Gulf of Aden, one of the globe's busiest maritime trade routes.

Pirates have since redeployed to the Indian Ocean, a much wider area very difficult for naval forces to patrol effectively.

Since the start of October, subsiding monsoon winds have allowed pirates equipped with small skiffs to resume their operations in earnest after a lull that had seen the number of hijacked vessels drop to two.

Among their latest catches are an Indian cargo ship, a Spanish trawler with a crew of 36, a Singapore container ship with 21 crew members and a Chinese bulk carrier with a crew of 25.