KAMPALA, Uganda--Tanzanian troops and Ugandan rebels, showered with flowers by civilians, entered Uganda's capital in triumph yesterday after a five month war to drive dictator Idi Amin from power.

Residents of Kampala crowded the streets to greet their "liberators," climbing on Tanzanian tanks, looting shops and beating to death stragglers from Amin's army.

Amin and remnants of his forces were last seen Tuesday fleeing eastward toward Jinja, 50 miles away, in a convoy of limousines. Some reports said he had gone to Tototo, near the Kenyan border.

Townspeople in Jinja reported a flood of wounded soldiers from Amin's loyal units. Tanzanian and rebel commanders ordered no immediate full-scale push to the east, however.

"The racist fascist is no longer in power!" the rebels said yesterday in Uganda Radio broadcasts and through loudspeakers in Kampala streets.

In Washington, U.S. officials welcomed the ouster of Amin and said the United States would move quickly to establish a normal relationship with the new government.

The officials, who asked not to be identified, said the Carter administration, in anticipation of Amin's downfall, began consultation with Congress 10 days ago on lifting restrictions on U.S. economic aid to Uganda.

They also said U.S. officials contacted members of an Ugandan exile government coalition group.

The Tanzanian-sponsored Ugandan National Liberation Front quickly announced establishment of a provisional government with former Ugandan university official Yussufu K. Lule as president, defense minister and armed forces chief.

In a broadcast statement from Dar es Salaam, Tanzania, Lule promised a "rule of law" and said Uganda's first elections since 1962 would be held "as soon as conditions permit." Lule said he wants to "bring back to the people of Uganda the good life they once knew." "There must be no revenge," Lule added.