Russian investigators say they are trying to identify the woman they suspect launched a suicide attack on a minibus in the North Caucasus.
Twelve people were killed in Thursday's attack in Vladikavkaz, the capital of North Ossetia. Officials believe one of them was a female suicide bomber.
The device exploded as the minibus stopped near a busy market.
North Ossetia has, like neighbouring Ingushetia and Chechnya, suffered sporadic violence from militant groups.
While Chechen rebels have used suicide bombing in the past, the tactic has not been used much in recent years in Russia.
The explosion happened at about 1415 local time (1115 GMT) on Thursday, as passengers were getting off the packed minibus, Russian officials say.
"As of now, 11 people have died. All have been identified," local government health minister Vladimir Lekoyev told the AFP news agency, adding that this figure did not include the suspected bomber.
An investigator with the prosecutor's office told AFP that they were trying to identify the severed head of a woman, suspected of being the bomber.
"We are trying to create a photo-fit. All that's left is the head," the official said.
A video camera in the square showed the explosion occurred as a woman was boarding the bus, he added.
Some 35 people remained in hospital on Friday morning, the Itar-Tass news agency reported.
They included a girl said to be in a life-threatening state.
Many of the injured are young students who were on their way home when the blast occurred, the agency said.
So far nobody has claimed responsibility for the explosion.
North Ossetia was the scene of the Beslan school siege in 2004, when pro-Chechen militants seized schoolchildren and teachers. It ended with more than 300 people dead after a bungled assault by Russian troops.
Neighbouring Ingushetia suffers almost daily shoot-outs and explosions.
The Georgian breakaway region of South Ossetia - scene of a brief war between Russia and Georgia in August - also borders on North Ossetia. Thousands of Russian troops remain in South Ossetia.
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