A suspected female suicide bomber today killed 11 people and wounded as many as 40 others in an attack in Russia’s restive North Caucasus.

The bomber struck as passengers were leaving a minibus at a bus stop next to the central market in Vladikavkaz, capital of the North Ossetia region, officials said.

Russian television showed the shattered vehicle with windows blown out and the corpses of several people lying among apples scattered on the ground around it. One woman was covered by a pink sheet with her handbag on top.

President Medvedev ordered police and the Federal Security Service (FSB) to tighten security in the region, which borders South Ossetia, the focus of the war between Russia and Georgia in August.

“According to preliminary information, the explosive device at the bus stop in the centre of Vladikavkaz was activated by a female suicide bomber,” a statement by the regional administration said.

The North Ossetian President Taimuraz Mamsurov said later that the severed head of the alleged bomber had been recovered.

Initial reports suggested that an exploding gas canister could have caused the tragedy, although local officials later rejected this explanation. Many vehicles in the region run on gas instead of petrol.

Vladikavkaz is only a few miles from Beslan, scene of the school siege in 2004 that claimed the lives of more than 300 people taken hostage by Islamist separatists, including female suicide bombers, from neighbouring Chechnya.

North Ossetia has a mainly Christian population and shares a border with South Ossetia, which was recognised as independent by Russia following the war with Georgia in August.

South Ossetians have made no secret, however, of their desire to unite with their ethnic kin inside Russia.

There have been growing concerns over instability in the North Caucasus in recent months. Analysts have suggested that Russia’s decision to recognise South Ossetia and Georgia’s other breakaway region of Abkahzia has provoked a resurgence in separatism within its own borders.

Seven police were wounded in two bomb blasts in Ingushetia on Sunday, days after President Medvedev dismissed the region’s unpopular ruler for failing to defeat a growing insurgency. Russia fought two bloody wars to suppress rebellion in neighbouring Chechnya after the collapse of the Soviet Union in 1991.

A car bomb killed seven soldiers last month outside Russia’s military headquarters in South Ossetia. Russian and Georgian officials accused each other of carrying out a terrorist bombing to wreck the ceasefire that ended the war.

North Ossetia has declared Saturday a day of mourning for the victims of the bombing.

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