Russian authorities were scrambling Tuesday to contain a major oil spill on the Volga River after a barge ran aground when its captain fell asleep.

The barge spilled two tonnes of oil products into Europe's longest river when it ran aground early Monday, creating a 12-kilometre (7.5 mile) slick, the emergency situations ministry said.

"It was early morning and the captain fell asleep," Russian television said.

Some 140 people and 40 equipment units, including a helicopter, have been involved in the operation to contain the slick, the ministry said in a statement Tuesday.

A resident from the town of Oktyabrsk in the Samara region in central Russia complained that the spill has prevented locals from swimming.

"We drove up and took a look. Indeed, you can't swim," television cited Sergei Kazakov as saying.

The barge contained a total of 190 tonnes of oil products.

The captain only contacted the emergency situations ministry an hour and a half after the incident took place, the television report said. The ministry did not say whether wildlife had been affected.