A ferry stranded in the Baltic Sea for about six hours with an estimated 300 people on board has safely reached its destination, port authorities say.

The ferry, operated by Copenhagen-based DFDS Seaways, was in international waters off Kaliningrad, a Russian coastal enclave between Poland and Lithuania, when the engine stopped working.

Smoke poured out of the engine room and triggered the fire extinguisher inside the room, the ferry operator said.

The breakdown paralysed the boat for about six hours.

Port spokeswoman Dovile Ringis told reporters the ferry reached the Lithuanian port of Klaipeda at 9.30pm, powered by its own engines despite strong wind and waves.

It was escorted by Lithuanian navy ships dispatched as a precaution with emergency crews on hand at the port, she said.

Earlier, passengers had assembled at muster stations in preparation for a possible evacuation, and rescue ships were scrambled as a precaution.

But an evacuation order never came, and there were no reports of injuries.

“We are talking about a malfunction in the engine room that caused a lot of smoke,” DFDS spokesman Gert Jakobsen said.

The ferry, which also carried cars and trucks, was traveling from Kiel, Germany, to Klaipeda, which is north of Kaliningrad.

The crossing normally takes about 20 hours.

“On these kinds of crossings we have people from Germany, the Baltic countries and Russia. We cannot say now who was onboard,” Mr Jakobsen said.

The ship is about 85 kilometres (50 miles) from Klaipeda, said Vaidas Klumbys, another DFDS spokesman.

He said on Tuesday afternoon: “We received the information from the ship that it was undergoing vibrations and smoke rising from the engines”.

Russian state news agency Tass quoted Andrei Permyakov, head of the sea rescue co-ordination centre in Kaliningrad, as saying that rescuers from Lithuania, Russia and Poland responded.

Lithuania’s navy said one of its helicopters and three navy vessels were sent to the site in case an evacuation was necessary.

The regional news agency Baltic News Services quoted Mr Klumbys as saying “the weather conditions are not good”.

Mr Jakobsen was not aware of any rescue operation, saying there was no evacuation.

“But in this kind of situation, everyone steps in,” he said.

The Regina Seaways was built in 2010 and can carry up to 500 passengers.