LONDON: A three-metre minke whale calf was refloated early on Monday after it was found injured and beached on concrete in the River Thames just west of London but the animal's life hangs in the balance as it is so young and so far from home.

A special team of rescuers from Port of London Authority, Royal National Lifeboat Institute (RNLI), British Divers Marine Life Rescue, London Fire Brigade and the police worked for hours through the night to refloat the whale.

By around 0000 GMT, they got the whale onto a special inflatable pontoon and towed it a mile downstream from Richmond Lock. The whale then slipped off the pontoon and was last seen freely swimming in the river.

"It is a mild success in the sense that the animal is no longer trapped on concrete - but that whale's life hangs in the balance: it is injured, it is very young and it is so far from home," Martin Garside, a spokesman from Port of London Authority, told Reuters.

"This animal comes from the northern North Sea - so it is hundreds of miles where it should be. The whale is a hundred miles from the opening to the North Sea in the Thames Estuary," he said. "There is no obvious sign of his mother."

The common minke whale is the smallest of all baleen whales, reaching around 8 to 9 metres long. The whales prefer cooler temperatures and enjoy a varied diet of krill and schooling fish, according to the Whale and Dolphin Conservation group.

The do not usually appear in the River Thames.