Rescuers carry the bodies of victims from a ferry tragedy near Zanzibar Island at Nungwi Beach September 10, 2011.[Photo/Agencies]

STONE TOWN, Zanzibar - At least 107 people drowned when a ferry capsized in rough waters off east Africa as it sailed from Zanzibar to Pemba island, a doctor said on Saturday, the worst disaster in the archipelago's recent history.

Witnesses fear the death toll could rise sharply since the vessel was carrying well over 500 passengers and only 260 survivors have been found so far by fishing boats and tour operators scouring the sea since the early hours.

"We are still receiving many bodies by truck loads ... The death toll will likely be much higher," doctor Karim Zah of the Mnazi Mmoja Hospital in Zanzibar told Reuters.

Dozens of soldiers carrying bodies onto shore dotted the white sand beaches at the northern tip of Zanzibar island where thousands of people anxiously awaited news of survivors.

A stream of military trucks brought in bodies to the Maisara football grounds in Stone Town, where tens of thousands of people gathered to identify the dead.

Emergency workers covered bodies in dark blankets and placed the victims' clothes on top so relatives could identify them.

At the popular tourist destination of Nungwi, fishing boats and diving vessels ferried survivors ashore, a dozen or fewer at a time, and crowds waded waist deep in the water as the boats approached shore, desperately searching for relatives.

Zanzibar, also know as Unguja, and Pemba are the two main islands of the Zanzibar archipelago, a popular destination for tourists visiting their pristine Indian Ocean beaches.

Zanzibar is a semi-autonomous region of the east African country of Tanzania.

"The ship's manifest shows that the vessel travelling from Unguja to Pemba islands had more than 500 passengers on board," said Zanzibar Police Commissioner Mussa Alli Mussa told Reuters.

"Some 260 passengers have so far been rescued ... we have recovered several bodies but I can't give you the exact death toll at the moment because the situation is very volatile," he told Reuters.

Tour operators and local diving instructors spent the night at sea searching for survivors.

"FEARING THE WORSE"

"Many of us got here about 2.30 a.m. (2330 GMT) this morning," said Suleiman Amis, 32, who works on a local diving tour boat. "We sent out some boats to search for the survivors, but we did not find them until very, very late."

"We have friends who we know took that boat and we want to go back out to find them as soon as possible," he told Reuters.

Pemba is about 40 km (25 miles) from Zanzibar. Passengers who regularly take ferries between the two islands said the vessels are in a poor state of repair and are often overcrowded and loaded with cargo.

Abdual Said, registrar of Zanzibar's seafaring vessels, told Reuters the capsized ferry, MV Spice, was licensed to carry 600 passengers.

"They normally pack us in like sardines in a can. And for that I really fear this could be a very big disaster," said resident Mwnakhamis Juma.

The government in Zanzibar said last month it planned to invest in bigger, more reliable vessels to ferry passengers between the two islands. Zanzibar's cabinet was meeting on Saturday in response to the disaster.

"We are fearing the greatest calamity in the history of Zanzibar. This is a disaster," said a government official, who declined to be named.

Two small overloaded boats capsized and were swept away in high seas off Tanzania's coast in January this year and in May 2009, a vessel just off Zanzibar sank with dozens aboard, killing six.

Police commissioner Mussa said rescue workers with the aid of some fishing boats in the area were helping to rescue more passengers and recover bodies to bring them to Zanzibar's main town for post-mortems and identification.

"Because of strong ocean winds, some of the bodies could even be washed up in Tanga (mainland Tanzania)," he said. "The cause of the accident cannot be confirmed at the moment."

A parent in Mkoani on Pemba island was already mourning his three children, who were aboard the capsized ferry.

"I had two sons and a daughter coming back to Pemba from a school holiday break ... and I am fearing for the worse," said Juma Bakar.