News agencies on Wednesday, quoting the Kremlin press service, said: "The [Russian] president has ordered the special forces to take all necessary measures to find and destroy the criminals who killed Russian diplomats in Iraq."

The embassy employees were seized in Baghdad on June 3 when armed men attacked their vehicle. A fifth Russian citizen was killed during the kidnapping.

Moscow confirmed that the four men were dead after a video footage apparently showing two men being killed appeared on the internet on Sunday.

An anti-government coalition led by al-Qaeda in Iraq - the Mujahidin Shura Council - has said they were responsible for killing the men.

Putin also said Russia would be grateful for any information on the killers.

Duma condemnation

Earlier on Wednesday, the lower house of the Russian parliament condemned the murders and criticised the "occupying powers" in Iraq for losing control of the country.

The statement, passed 425-0 by the State Duma, "deplores the death of our compatriots ... expresses profound indignation over the fact of their brutal murder and strongly denounces the criminals, who committed that heinous crime".

The four embassy workers were
seized by armed men in Baghdad

It says the abduction and killings were possible because "of the deepening crisis in Iraq, while the occupying countries are losing control over the situation, and terror and violence are becoming the order of the day in that country".

The statement also demanded that Iraqi authorities and foreign forces conduct a thorough investigation into the deaths.

The kidnappers had demanded that the Kremlin pull its soldiers out of Chechnya, a predominantly Muslim region in southern Russia where separatists have been fighting for independence.

Russia strongly opposed the US-led military campaign in Iraq.