A suicide bomber has killed four police officers and wounded a further five people in the provincial capital of Chechnya.

Russia's interior ministry said the attacker detonated explosives outside its main headquarters in Grozny.

Last month, the Kremlin formally ended a federal counterterrorism operation in Chechnya, which has experienced two bloody separatist wars in the past 15 years.

But insurgents continue to stage frequent attacks on troops and authorities in the region despite increased stability under Kremlin-backed regional President Ramzan Kadyrov.

Mr Kadyrov praised the policemen who died, saying their courage helped prevent higher casualties. He sought to downplay the attack and insisted that it wouldn't disrupt efforts to stabilise the region.

"The incident had no impact on the situation in Grozny," Mr Kadyrov said. "The situation in the capital and on the entire territory of the republic is absolutely calm."

The wars in Chechnya have spilled over into persistent tension and violence in other provinces in Russia's north Caucasus.

In Kabardino-Balkaria, west of Chechnya, a top official at a jail holding defendants on trial over a 2005 attack was shot dead in the street yesterday evening, officials said.