The Kremlin-backed president was among those killed in a bomb attack in the capital, Grozny. Mr Abramov, who was in Moscow at the time, is reported to be consulting his cabinet about how to respond.

Russian President Vladimir Putin vowed revenge for the bombing, which is being blamed on Chechen guerrillas. The estimated death toll varies between six and more than 30. About 50 are thought to have been wounded.

Security forces throughout Chechnya have been placed on high alert and Russia's Itar-Tass news agency has reported that five people have already been detained on suspicion of involvement with the attack, according to interior ministry officials.

Mr Kadyrov was fatally wounded when a device exploded during a ceremony marking victory in World War II. The bomb went off in a VIP seating area of the packed Dynamo stadium in Grozny.

?Retribution is inevitable?

There is uncertainty over the fate of the commander of Russian troops in Chechnya, Gen Valery Baranov, who was also in the stadium at the time. Officials have denied reports that he was killed by the blast and said he was fighting for his life in hospital.

Russian television showed chaotic scenes as panic-stricken spectators ran from the scene and brown smoke rose from the debris of the stand. One man was seen carrying an injured child to safety, while bursts of gunfire rang out.

The emergency ministry spokesman said a second device had been found following the evacuation of the stadium. Chechen interior ministry officials said at least 32 people had been killed ? however other reports put the death toll at six.

Mr Putin, speaking at the end of the Victory Day parade in Moscow, said: ?There can be no doubt that retribution is inevitable for those whom we are fighting today. It will be unavoidable for terrorists.?

He said Mr Kadyrov's work had proven there was a difference between ?bandits, terrorists and the Chechen people?. Russia has been fighting separatists in Chechnya since the republic first tried to break away in the 1990s.

Moscow has reimposed its rule in Grozny, but rebel attacks have continued, both in Chechnya and elsewhere in Russia. Mr Kadyrov's assassination has drawn broad international condemnation.

A White House spokesman said Washington resolutely rejected all acts of terrorism, while the European Commission described the blast as a ?heinous attack?.