Story highlights Floods swept through parts of the city; rain continues

More than double the average monthly rainfall falls in 48 hours

Slow-moving weather system has spawned tornadoes in Italy, Greece, and Turkey

A day of mourning has been declared; at least 11 die

At least 11 people have died in Varna, the largest Bulgarian city on the Black Sea, as a result of massive flash flooding and mudslides, the Interior Ministry said.

Some of the victims are children, the ministry said. Dozens were still missing, and tens of thousands were without electricity, the ministry said.

The floods swept through parts of the port city Thursday and the rains continued Friday. City boulevards and streets have turned into rivers and many of the pedestrian underpasses are completely flooded.

The heaviest hit district is Asparuhovo, where most of the streets are impassable, filled with smashed and overturned vehicles and uprooted trees.

Some 4.3 inches of rain, more than double the monthly average, fell in Varna in a 48-hour period.

The weather system responsible for this flooding has been progressing very slowly across southern Europe this week, and has spawned tornadoes in Italy, Greece, and Turkey, including near Istanbul.

The storm system was beginning to move off to the northeast, but some more light rainfall was expected for eastern Bulgaria for the next 24 hours or so.

Bulgarian authorities have declared an emergency in the region.

Friday was declared a day of mourning for the victims.