TWO British soldiers are missing in southern Iraq, and several US marines have been killed in fighting around the city of Nasiriyah, in what has been described as the toughest day so far in the war in the Gulf.

The Ministry of Defence would give no details of the unit the missing British troops were from, or where they had been operating when their vehicle came under attack.

Saddam Hussein today gave a defiant speech in which he said the Iraqi people were "proving their bravery against the enemies of humanity".

He claimed that victory was near in Basra and called on troops to hit the coalition forces "wherever they are".

Meanwhile Iraqi television were showing what they claimed was a downed Apache helicopter.

Reports differed on how many US marines had died in Nasiriyah, where their units faced strong resistance while fighting their way the city to capture two bridges, one over the River Euphrates and the other over a canal.

One report said six marines had died and 14 had been injured, but others put the figure of dead at seven or even "up to ten", with 25 injured.

There were also reports that a chemical weapons factory may have been found by US troops near the city of Najaf.

American Lieutenant General John Abizaid said yesterday (sun) had been the toughest day of the war and the fighting around Nasiriyah had been its "sharpest engagement".

But he said Allied forces would be at the outskirts of Baghdad "soon".

Also in the Nasiriryah area 12 US personnel, apparently from a maintenance unit, were reported missing after their convoy was ambushed.

Five US troops - four men and a woman - who apparently were taken prisoner from this group, were shown being questioned on Iraqi TV, drawing condemnation from George W Bush and Tony Blair.

The Americans said showing their captured personnel on television was a breach of the Geneva Convention, though the Iraqis later said they were abiding by the convention.

Some American military officials have blamed the rapid progress of their forward units for some of the problems their forces have encountered in areas which were supposed to have been secured, such as the road where the maintenance unit was captured.

Some Iraqi fighters appear to have turned to guerrilla-style warfare, operating behind the Allied advance columns, sometimes in civilian dress, posing a particular hazard in urban areas.

A US convoy is now heading for Baghdad from the Basra area, where fighting continues, as it does in the southern port of Umm Qasr, which was reported captured on Friday.

Huge explosions were reported in the centre of Baghdad at about 12.10am today.

Meanwhile the body of ITN reporter Terry Lloyd has been found near Basra, following a possible "friendly fire" incident.

And the two crew of a Tornado from RAF Marham in Norfolk, which was struck by a US Patriot missile while entering Kuwait airspace, are believed to be dead.

Protests against the war continued in Britain, with about 1,000 demonstrators converging on the Menwith Hill "spy base" near Harrogate for a largely peaceful event, though a dozen people were arrested.