A humpback whale stranded on Germany’s Baltic Sea coast since early this week has freed itself and swum into deeper waters, rescuers said on Friday.

A flotilla of vessels were following the weakened animal at a distance, hoping to help guide it into the North Sea and toward the Atlantic Ocean, its natural habitat.

The roughly 10-metre-long (33ft) sea mammal was first spotted on Monday stuck in shallow water off Niendorf near the northern city of Lübeck.

Then commenced days of intensive efforts to free the whale using boats to make waves and excavators to dig up sand, as fears grew for its life.

Rescue teams on Thursday began using earth-moving equipment on a pontoon to dredge a channel through the sand to give the animal a route to escape.

Then, overnight to Friday, the whale “gathered its forces” and “freed itself using its own strength”, the marine biologist Robert Marc Lehmann said.

“Whale rescue successful,” he wrote on his Instagram profile.

However, he cautioned against premature celebration and said the animal was “very ill” and had a long way to go before reaching “its real home, the Atlantic”.

The whale had been entangled in a fishing net, most of which rescuers managed to remove.

Lehmann said the whale was “zigzagging” in the water and could become stranded again.

Experts from the marine conservation group Sea Shepherd also warned that the whale had a skin disease.

The animal was being escorted by, among others, two vessels from the Schleswig-Holstein state water police, a spokesperson from its headquarters in Kiel told AFP.

Experts hope it will swim back to the North Sea through the straits between Germany, Denmark and Sweden and on to the Atlantic Ocean.

“Now we just have to hope that it finds its way out,” the state premier, Daniel Günther, said on local radio, thanking the rescue volunteers.

“I think they were all happy that all their digging had finally paid off.”