A young woman set herself on fire in the central Bulgarian town of Stara Zagora on Monday, the fourth self-immolation in the country in just over a month, hospital sources said.

The 32-year-old woman was hospitalized with 92-percent burns, and local emergency hospital chief Chavdar Popov described her chances of survival as "minimal."

Bulgarian prosecutors on Wednesday charged a controversial imam and six others with inciting jihad and accused the group of serving as a link for Westerners seeking to join Islamic State fighters.

Ahmed Mossa Ahmed, a Bulgarian imam in a tight-knit Roma neighborhood in southern Bulgaria, was detained Tuesday along with five men and one woman in a massive operation by police and prosecutors that included a raid on a mosque.

Bulgarian right-winger Boyko Borisov said Tuesday he would form a minority government after failing to form a coalition following elections this month, warning that yet another vote would be "fatal" for the EU's poorest country.

Talks with other parties "made it clear that the only possible formula for a government... is to form a minority coalition between (his party) GERB and the Reformist Bloc," Borisov told journalists after negotiations in Sofia.

President Vladimir Putin accused his US counterpart Barack Obama of a hostile approach towards Russia, warning in a Cold War-style tirade that Moscow would not be blackmailed by the West over Ukraine.

Putin fired off his combative comments shortly before he arrived amid tight security to a red carpet welcome in Belgrade, seeking to cement Russia's influence in its loyal European ally.

Bulgarians voted Sunday in elections expected to result in a remarkable comeback for strongman Boyko Borisov, less than two years after mass protests in the EU's poorest member caused his resignation.

Time will tell however whether the right-wing former bodyguard will be able to implement painful reforms and restore voters' tattered trust in democracy by tackling rampant corruption, organised crime and cronyism.

Bulgarian President Rosen Plevneliev denounced Russia's Vladimir Putin as an aggressive leader with a 19th-century empire-building style, in comments to be published Saturday.

"Russia is a nationalistic and aggressive state," Plevneliev told Germany's Frankfurter Allgemeine Zeitung.

Fifteen people were confirmed dead on Thursday in a blast that flattened a Bulgarian explosives decommissioning plant near the northwestern village of Gorni Lom the previous day, officials said.

"Thirteen men and two women perished. The blast was so powerful that it left craters," civil defense force director Nikolay Nikolov said, adding that the cause was probably "human error."

Fifteen people were feared dead Thursday after a blast flattened a Bulgarian explosives plant that decommissioned landmines, with the government saying there was "minimal" chance of finding survivors.

"There are no signs of life at the site of the explosion" that ripped through the plant near the northwestern village of Gorni Lom late on Wednesday, civil defence force director Nikolay Nikolov told local radio.

Two people drowned and 900 were evacuated from their homes as flooding caused by torrential rains hit northwestern Bulgaria, the latest in a string of such disasters since June, the interior ministry said on Sunday.

Over 800 residents of the town of Mizia were evacuated overnight and during the day on Sunday after the swollen river Skut submerged large parts of the town under up to three meters (10 feet) of water, the interior ministry said.

Russia has asked Bulgaria to extradite a prominent opponent of Russian President Vladimir Putin who was arrested at Sofia airport, the Bulgarian prosecution announced on Thursday.

Nikolay Koblyakov, founder of the French non-governmental organisation Russie-Liberte which had staged a series of anti-Putin actions in France, was detained on an Interpol warrant at Sofia airport on Tuesday and held for 72 hours, the interior ministry said.