Navy ships and aircraft intensified the search for 12,000 or more persons reportedly missing as a result of the severe cyclone and tidal wave that swept over coastal Bangladesh early Saturday in the most devastating natural disaster since the country won independence 13 years ago.

An estimated quarter of a million persons, many of them fishermen and rice farmers who settled in thatched huts on relatively new islets created by silting in the Ganges River delta, were believed to be left homeless by the high winds and waves reaching 45 feet that swept over seven islands in the vicinity of Chittagong, in southern Bangladesh.

A spokesman for the disaster control center here was quoted by news agencies as saying 3,000 bodies had been recovered and that at least 12,000 were still missing. A district administrator's report gave the official death toll of identified victims as 1,302.

Eyewitnesses returning from the relief operations said that the delta and land on the Bay of Bengal were littered with thousands of bloating cattle, creating potential health hazards to the survivors.

The Bengali-language daily, Ittefaq, reported that hundreds of survivors were clinging to bamboo rooftops of their destroyed homes in water infested by sharks and crocodiles.

In Geneva, the International Committee of the Red Cross appealed for $1.7 million to aid the victims, saying it had an official death count of 3,000, news services reported. The Red Cross said it had unconfirmed reports of 40,000 dead in the storm, but "we discount these at the present time."

In Washington, the American Red Cross relayed an appeal from the Bangladesh Red Cross for $2 million for the initial relief for 120,000 persons. Joe Carniglia, director of international services, said the figure will probably go up once the magnitude of the disaster is known. He asked that contributions be made to local chapters of the American Red Cross.

Meanwhile, the State Department said the United States was making $25,000 available immediately for the relief effort. "We're waiting for more detailed information before reassessing the situation," said duty officer Vivian Ascher.

Bangladesh's martial-law leader, Lt. Gen. Hussein Mohammed Ershad, who toured the stricken area by helicopter today, told reporters it was the "worst tragedy in Bangladesh's history." In 1970, the year before the country was created out of East Pakistan, tidal waves during a cyclone killed as many as 100,000 persons, and in May 1963, about 25,000 persons perished in another cyclone.

Bangladesh radio today put the total death toll at about 100,000 for all of the seven stricken islands, but there was no confirmation of that figure by rescue workers and the government.

Of the seven most affected islands, three had been formed within the past decade and only relatively recently became inhabited by fishermen and mainland farmers who had been displaced by steady erosion of the river banks.

In a briefing of correspondents tonight, Col. Abu Nayeem Amin Ahmed, staff officer of the martial-law secretariat, said that the population of one of the islands, Urirchar, was estimated at from "a few thousand" to 10,000, and that it was feared that all were drowned in the 12-foot tidal wave. He said all of the livestock on the island was destroyed and 80 percent of the homes lost.

Ahmed said the population of the island, about 20 square miles in size, fluctuates because when the tide is low during the dry season farmers walk through waist-deep water to the island from the coastline to graze their cattle but return to the mainland at intervals. The transient population is not registered or even counted by local authorities he said.

Also, Ahmed said, "so many people went to fish and are not coming back. Until families are reunited, we cannot say who is missing or lost." Because of the remoteness of the area and disruption of communications, there were a number of stricken localities that even district government authorities were unable to reach. A disaster control center official said it may take rescue workers two or three days to reach those areas.

Six Navy ships were reported to be plowing through heavy seas to reach the islands, and Air Force helicopters ferried in medicine, food and other supplies to the survivors.

Ershad visited Urirchar today in his personal helicopter and, according to press secretary M. Tajul Islam, personally supervised the burial of two victims. The state-run television showed film of the president feeding water and biscuits to children and handing out clothing to other victims.

An official at the disaster control center said that in 21 subdistricts in the Chittagong and Cox's Bazar area alone, half the dwellings and 80 percent of the crops were destroyed by the tidal wave and winds estimated at close to 100 mph.

Authorities said that among the missing are fishermen who had been out to sea when the cyclone struck and farmers who may have tried to flee to safety by boat as the storm developed.

Disaster control officials said the worst affected islands were Urirchar, Sandwip, Char Clark and Atiya, all located west of the port city of Chittagong. They said that Chittagong, for the most part, escaped damage as the cyclone pushed a huge tidal wave northeastward.

Authorities said 217 persons were reported to have died on Sandwip Island, which early news agency reports said had been devastated by the tidal wave at a loss of 10,000 lives.

Ershad called off a state visit to China scheduled for Wednesday.