A deadline to execute two Bulgarian hostages being held in Iraq has passed without news of their fate.

The men, two civilian truck drivers, are being held by a group headed by militant Abu Musab al-Zarqawi. The radicals, the Tawhid and Jihad group, were responsible for the beheading of the American businessman Nicolas Berga and South Korean translator Kim Sun-Il.

The captors, loyal to insurgency leader Abu Musab al-Zarqawi, have threatened to execute the Bulgarians unless the US frees all Iraqi detainees.

A video aired by al-Jazeera late last night showed the two Bulgarians sitting down with their hands tied, while three armed masked men stood behind them.

The two have been identified as Ivaylo Kepov and Georgi Lazov from the town of Boboshevo and Georgi Lazov from the town of Blagoevgrad. The two Bulgarians were reportedly held captives near the northern town of Mosul and later their location was not known.

They were working for a haulier company with headquarters in Blagoevrgad, Western Bulgaria.

The video showed the two Bulgarians sitting with their hands cuffed, surrounded by three armed masked men. One of the men read a statement, though his voice could not be heard. Voices couldn't be heard, but analysts managed to read the lips of one captive.

"The group said the Bulgarian government bore responsibility over the safety of its citizens because it has sent troops to Iraq," the television added.

The insurgency group is also believed to be behind a number of attacks on police and security forces in Iraq that claimed the lives of 100 people just before the coalition forces' handover of power to an Iraqi interim government last month.

Bulgaria has a 485-member battalion in Iraq, which serves alongside Ukrainian troops under Polish command.

Bulgarian officials are continuing in their efforts to free their citizens kidnapped in Iraq by suspected insurgents.

Bulgarian President Georgi Parvanov gave an exclusive interview to Qatar-based TV station Al-Jazeera appealing to the militants to free the Bulgarian men, as their claims are not addressed to Bulgarian people and state.

The latest kidnap came hours after a Lebanese-born US marine who was allegedly kidnapped in Iraq, turned up in the US embassy in Beirut.

Iraq captors holding a Filipino hostage have threatened to kill him unless Manila withdraws its troops from Iraq within 72 hours.

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