'Black widow' bomber attacks Russia police
A suicide bomber has blown herself up in the capital of the troubled southern republic of Dagestan, Makhachkala, officials say.
Fifteen people including five policemen were wounded in the attack, close to an interior ministry building.
Some of the victims were seriously hurt and at least one of the police officers was in a critical condition.
In recent years, Russia has seen a number of attacks by women suicide bombers, known as black widows.
They are often related to Islamist militants killed during a separatist campaign against Russia, particularly in the North Caucasus.
The bomber in Saturday's attack, aged 25, was also thought to have been previously married to at least one militant, Russian news agencies reported.
"She has already been identified as Madina Aliyeva, a widow. Her two previous husbands were also killed as members of militant groups," Magomedbek Akhmedov, a spokesman for Dagestan's president, told Russian TV.
Her first husband was killed in 2009 and her second husband in 2012, a source told Interfax news agency.
A picture said to be of Madina Aliyeva was broadcast on state TV, and Russia's National Counter-terrorism Commitee (NAK) said she had previously travelled abroad to contact illegal groups.
The bomber approached traffic police near the Dagestan interior ministry building shortly before midday (08:00 GMT).
The force of the blast was equivalent to around 500g (1.1lb) of TNT, officials said.
Russia's emergencies ministry was said to be preparing to airlift some of the victims to Moscow for treatment.
Dagestan, which borders Chechnya, has seen some of the worst violence in the North Caucasus. Four people were killed and many more wounded in two car bomb explosions in Makhachkala on Monday.
Mr Akhmedov said this week's attacks were "clearly" linked.
Dagestan was briefly home to the Boston bombing suspects, Tamerlan and Dzhokhar Tsarnaev. Tamerlan Tsarnaev, who died in the police operation to capture the brothers, made a lengthy visit to the restive republic last year.