British military commanders have condemned pictures apparently showing two dead British soldiers and two "British" prisoners of war broadcast on TV station al-Jazeera.
One of the alleged British prisoners of war on al-Jazeera TV
The Qatar-based channel showed the bodies of the soldiers lying in a dusty street and two prisoners in a room with Iraqis.
The Ministry of Defence later confirmed the dead men were thought to be two soldiers who had gone missing during fighting around the town of al-Zubayr, near the southern city of Basra.
Their families have been informed of the development.
A military spokesman said he was "shocked and appalled" by the broadcast and Prime Minister Tony Blair reacted with "horror".
One of the soldiers appeared to have been shot in the chest but the other's injuries were unclear.
Their wrecked vehicle was included in the footage, with armed civilians climbing over it.
They had been classified as missing after their Land Rover was ambushed on Sunday.
The commander of UK forces in the Gulf Air Marshal Brian Burridge said: "We are shocked and appalled by this flagrant and disgraceful breach of the Geneva Conventions.
"We deplore the decision by al-Jazeera to broadcast such material and call on them to desist immediately.
"All media must be aware of the limits of taste and decency."
Tony Blair's official spokesman said: "The prime minister's reaction was horror both at the deaths and at the fact
that the pictures were shown."
The MoD says it cannot confirm the nationality of the two captives shown in the TV footage.
Al-Jazeera said it believed they were Kenyans working for the British Army as truck drivers.
Shadow Foreign Secretary Michael Ancram said: "This is another blatant
example of the depths to which this regime is prepared to sink.
"Just as they have no compunction about murdering their own people in their
tens of thousands, their depravity knows no bounds in their treatment of
prisoners of war."
British forces were scrambled to attack a column of up to 120 Iraqi armoured vehicles, including tanks, from Basra towards the al-Faw peninsula.
The BBC's Clive Myrie said the marines - ill-equipped to deal with such a move - had called in Tornado and Harrier fighter jets from Kuwait which had been attacking the vehicles "with some success".
It was assumed the vehicles were staging a counter-attack on the British forces to recapture the peninsula, although they could have been fleeing amid a possible uprising in the city, he said.
UK Prime Minister Tony Blair said reports of overnight unrest in Basra were confused, but there appeared to be "some
limited form of uprising" against Saddam Hussein's regime in the city.
The BBC's Frank Gardner said investigations seemed to suggest there had been some sort of disturbance, probably involving food and lack of supplies, but it had been quickly quelled by the authorities.
British reporters with the UK troops said coalition forces continued to attack certain targets within the city.
Humanitarian concerns are mounting because parts of Basra's population have no electricity or water.