At least 12 people have been killed in an explosion at a petrol station in south Russian region of Dagestan, according to local officials.

The incident occurred in the city of Makhachkala, which sits on the coast of the Caspian Sea, on Monday evening.

A further 50 people were injured, regional governor Sergei Melikov said, and doctors and rescue workers are at the scene.

The cause of the explosion is not yet clear.

Pictures showed a large fire lighting up the night sky and a number of fire engines at the scene.

The fire covered an area of 500 sq m (5,380 sq ft), the regional emergencies ministry.

The ministry warned there was a danger of further explosions.

The Republic of Dagestan is one of 83 constituent parts of the Russian Federation and is the southernmost part of the country. Makhachkala sits around 1,600 km (1,000 miles) from Moscow.