MOGADISHU, Somalia (AP) _ After weeks of heavy rain, two rivers in southern Somalia merged to form an inland sea Monday, gushing over nearly 60 square miles and trapping thousands of Somalis without food.

One radio broadcaster reported that he was transmitting Monday while perched in a tree above swirling flood waters in the Bay region, 160 miles southwest of Mogadishu, the Somali capital.

Aid workers said water from the merged Juba and Shabelle rivers threatened eight regions.

At least 1,100 people have been confirmed dead since the flooding began a month ago, and an estimated 220,000 have been forced to flee their homes, according to Maria Frauenrath of the U.N. Humanitarian Affairs office.

Other aid workers say any estimate under 2,000 dead is conservative.

Some 2,500 people were stranded Monday on a dike near the port of Kismayo, where the Juba flows into the Indian Ocean, Frauenrath said.

``We fear these people might be swept away,'' she said, adding that so far rescuers only had two boats and were saving 20 people at a time.

Despite the severity of the flooding, the international community has been hesitant to begin a major aid mission in Somalia, where there has been no central government since armed factions ousted late dictator Mohamed Siad Barre in January 1991 then turned on each other.

A three-year U.S.-led effort to aid famine victims ended in disaster, with most participants pulling out by 1995.

Muslim preachers in Mogadishu appealed to wealthy Somali businessmen and traders to contribute to the relief effort, reminding them of their religious obligation to help brothers in need.

Meanwhile, more heavy rain was predicted in the central Ethiopian highlands, where the Juba and Shabelle rivers originate, according to the U.S. AID-funded Famine Early Warning System in Nairobi.

``We have had yet another very disturbing weather report, and that does not help us at all,'' said Wendy Driscoll, spokeswoman for CARE International.

Lynn Geldof, spokeswoman for the U.N. Children's Fund, said the first of four helicopters rented from a South African firm and 10 aluminum boats donated by Norway were expected to begin arriving in Nairobi on Wednesday.

The helicopters _ the only means of delivering relief supplies to the thousands stranded by flooding _ will be based in Garissa, near the Somali border in northeastern Kenya. They are being rented for a month at a cost of $1.7 million, because no international donor came forward to supply them, Geldof said.

``The terribly frustrating thing has been the drip, drip nature of the aid ... coming so slowly while people are literally clinging to trees to survive,'' she said.

The Red Cross has transported 160 tons of food and other relief supplies in the past week, using planes and trucks, agency spokesman Josue Anselmo said. But more roads and landing strips are being washed out daily by the floods.