The situation is such that the Indian Ocean archipelago risks becoming one of the world's most environmentally endangered island chains, they said, urging stepped up enforcement of and toughened ecological protection laws.

"Environmental destruction on Zanzibar is going from bad to worse," said Ali Juma, director of the environment department in the Tanzanian territory's semi-autonomous government.

"We must now review our policies and strengthen laws to control the situation," he told reporters here after the release last week of a UN report highlighting coastal pollution as a serious threat to the world's islands.

One of the main threats is the piping of untreated sewage from urban areas into the ocean, particularly around the capital where only 60 of the estimated 200 tonnes of solid waste produced daily are accounted for, officials said.

Last week, officials from the Institute of Marine Sciences at the University of Dar es Salaam told Zanzibari lawmakers that nearly 100 percent of raw liquid waste from Zanzibar town was being directed into the ocean.

Such disposals not only threaten marine life, but also damage beaches that have become an economic lifeline for Zanzibar while the islands aims to boost their reputation as an exotic world-class tourist destination, they said.

In addition to waste dumping, Zanzibar's coastal areas are in danger from the loss of mangrove forests and other trees at the hands of illegal loggers and hotel and home development too close to beaches, the officials said.

Regulations barring construction within 30 meters (yards) of beaches are routinely ignored and must be enforced and tightened if the islands are to avoid catastrophic damage, they said.

"The policies and laws have never been seriously implemented," said Asha Khatib, a senior researcher with the environment department, lamenting that 1992 and 1996 legislation is inadequate to protect delicate eco-systems.

He said that apart from infrequent nominal fines on locals for cutting down trees for firewood and rare cases of injunctions issued to stop beach-front construction, the government has not acted decisively to halt destruction.

On Thursday, the UN Environment Programme (UNEP) issued a new report saying that coastal pollution is threatening the recovery of coral reefs already damaged by rising sea temperatures blamed on climate change.

Healthy reefs are essential to maintaining the delicate environmental balance in the world's oceans and are estimated to bring in 30 billion dollars (24 billion euros) in revenue to local fishing and tourism industries, it said.

Tourism on Zanzibar, renowned for its exotic history as a hub for the spice and slave trades, has grown to a 55-million-dollar (45-million-euro) a year industry, representing 21 percent of the islands' gross domestic product.

The sector directly or indirectly employs nearly 45,000 of Zanzibar's some one million people and is hoped to surpass agriculture, currently 35 percent of gross domestic product, as its leading revenue earner by 2015.

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