Abdul Rauf Nassib and Egyptian Sayyed Imam Sherif were arrested with about a dozen other militants in the remote Lawder area, they said.

Troops backed by tanks and helicopters launched the raid on Wednesday.

The US is helping Yemen - which has suffered its own terror attacks - to track down militants.

Officials said security forces continued to surround a hideout where dozens of militants were believed to be sheltering near Lawder, 470km (290 miles) south of the capital, Sanaa.

The Yemeni opposition party al-Islah said the men had been given until Friday to "surrender unconditionally or face a military assault", the AFP news agency reported.

Prison break

Mr Nassib is reported to have been Mohammad Hamdi al-Ahdal's bodyguard.

YEMEN WAR ON AL-QAEDA Mar 2004: Abdul Rauf Nassib and Sayyed Imam Sherif among more than a dozen militants arrested Jan 2004: Yemen announces detention of al-Qaeda suspect Jaber al-Baneh wanted by US Nov 2003: Al-Qaeda leader Mohammed al-Ahdal arrested Sept 2003: Riyadh bombing suspect Bandar al-Ghamdi arrested Apr 2003: Al-Qaeda suspect Fawaz Yahya al-Rabeei arrested Nov 2002: Six suspected al-Qaeda members killed in US missile strike

He is alleged to have helped 10 militants suspected of involvement in the bombing of the USS Cole off the coast of Yemen in October 2000, to escape from Aden prison in April 2003.

Last November, Mr Nassib was the sole survivor of a US missile attack on a car, which killed six suspected al-Qaeda members in eastern Yemen, officials said.

Sayyed Imam Sherif, who was also reportedly captured, founded the Egyptian Islamic Jihad group which al-Qaeda leader Osama Bin Laden's right-hand man, Ayman al-Zawahri, once led, according to the website of Yemen's ruling party, GPC.

Yemen has stepped up its operations against Islamic extremists since the 11 September 2001, attacks on the United States, allowing US forces to enter the country and train with its military.