Russian President Vladimir Putin has vowed retribution after an explosion at a stadium in Chechnya's capital during a Victory Day parade killed Chechen President Akhmad Kadyrov.
Mr Kadyrov was the Kremlin's right-hand man in efforts to restore stability to the war-torn region.
Grozny's emergency medical centre said 24 people were killed and 46 wounded in yesterday's atrocity.
However, President Putin's representative in the southern Russian district, Mr Vladimir Yakovlev, said six people had been killed in the blast, the Interfax news agency reported. He said 53 people had been wounded.
The bombing harshly underlined the difficulties Russia faces in controlling the separatist region's violence despite a massive troop presence, and is expected to set off a new round of killing between Mr Kadyrov's camp and separatists who have long pledged to kill him.
The explosive is believed to have been a landmine planted under seats where Mr Kadyrov and other dignitaries were watching ceremonies marking the defeat of the Nazis in the Second World War.
There was no immediate claim of responsibility for the blast.
Police and soldiers began a search after the blast and detained at least five people, news reports said.
AP