Amid increasing indications that President Idi Amin's control is rapidly disintegrating, Tanzanian-backed Ugandan rebels speeded their drive today to capture the capital of Kampala and its international airport at nearby Entebbe.

There were conflicting reports from within the embattled East African country. Nevertheless, a picture emerged of chaos and retreat that pointed toward possibility that the struggle to end Amin's brutal eight-year-old rule is nearing a climax.

The Ugandan National Liberation Front, created several days ago with Tanzanian backing, issued a communique here saying Amin is fleeing with a protective convoy into his native northern Uganda. There was no confirmation of his whereabouts, but diplomatic sources reported that Libyan forces are grouping at Gulu, an air base 170 miles north of Kampala, with the apparent intention of assisting him.

The acceleration in Tanzanian and rebel plans to capture Kampala and Entebbe reflected a threat of increased Libyan help for Amin. Tanzanian President Julius Nyerere said the threat was made Tuesday by Libyan leader Muammar Qaddafi, but Qaddafi himself has never announced it.

"It's now a race between the antigovernment forces and the Libyans to see who gets there first," said one observer in Dar'es Salaam.

While often conflicting in specifics, reports reaching here today said Libya has escalated its airlift to help Amin repulse the rebel forces, said to be less than 10 miles from Kampala and Entebbe-within easy artillery range of both.

According to highly placed sources in the National Liberation Front, Qaddafi's reported threat to "fully" back Amin unless Tanzanian troops withdrew from Uganda within 24 hours has convinced the rebels to try to topple Amin as quickly as possible.

A well-informed Ugandan exile source explained: "We couldn't be expected to sit around idle while Qaddafi threatened to move in thousands of troops to fight us."

Until Tuesday, these sources said, the strategy had been to mass troops and equipment at Mpigi, a town on high ground 20 miles south of Kampala and Entebbe, and at a point about 20 miles west of the capital on the road to Fort Portal.

The plan was to delay any final assault until rebel forces were fully "Ugandized" to remove from Tanzania the stigma of felling with its own troops a fellow African government in violation of an important postcolonial African principle of noninterference. There also were hopes of waiting to install a provisional rebel government in "liberated" areas of southern Uganda.

Exile sources here have been saying for weeks that Amin is dispatching troops and supplies to his home area in the northern part of the country. One source commented today that Amin has turned Arua, his home town near the Sudanese and Zairean borders, into a "a huge PX," or post exchange, out with loyal forces.

Residents of Kampala and Entebbe, apparently anticipating a rebel attack, were reported fleeing in large numbers into the countryside and across the border into neighboring Kenya. Among those entering Kenya were dependents of U.N. personnel and the Saudi ambassador. There also were reports of gunfire and explosions in some quarters of Kampala and of the shelling of Entebbe. Observers here cautioned, however, that the confusion inside Uganda and the partisan considerations of rebel sources made all reports on the war subject to reserve. Foreign correspondents have not been allowed access to the war fronts.

Front sources have claimed anti-Amin forces number about 30,000, many of whom are concentrated around Kampala and Entebbe. The ratio between Tanzanians and Ugandans in the force is not known, but Tanzania has been reported to have between 4,000 and 5,000 of its own troops inside Uganda,

The Ugandan rebel forces, which late last month probably numbered several thousand, are said to have been expanded greatly by recruits from captured areas. In addition some of Amin's soldiers and scores of Ugandan exiles reportedly have been joining up.

Amin, even with Libyan help, is badly outnumbered. According to Nairobi diplomatic sources and sources inside Uganda, Between 500 and 800 more Libyan troops as well as equipment have been airlifted into Entebbe since Tuesday.The total number of Libyan troops in Uganda is said to be about 1,500.

Intelligence sources estimate Amin's army now numbers only about 2,000.

National Front leaders continued to meet here with a sense of urgency to make plan to move into Uganda, possibly in a few days. Military events seemed to run ahead of political preparation. Their plans only a few days ago had called for them to set up a temporary administration in the southern Ugandan town of Masaka.