Two members of the Nicaragua's ruling junta and a Cabinet minister have flown to Havana at the invitation of Cuban President Fidel Castro, Interior Minister Tomas Broge said today.

Junta members Alfonso Robelo and Moises Hassan and newly appointed Culture Minister Ernesto Cardenal left for Havana last night aboard a Cuban Airlines plane that flew in with 90 tons of food and a 60-member medical team to help in Nicaragua's reconstruction.

No mention of the visit - to attend celebrations of the 26th anniversary of the start of the Cuban revolution - was made at a joint news conference the five junta members held late yesterday.

Borge said members of the Nicaraguan government, which ousted Anastasio Somoza's government last week, would travel to any country that invites them.

Neighborhood teams formed by the new government began to rebuild Managua streets torn up in the fight to oust Somoza.

A government source said four Nicaraguan banks that were nationalized yesterday may reopen Monday.

Radio Sandino, official voice of the Sandinista guerrillas who drove Somoza into exile, has been urging neighborhood committees to form brigades to speed reconstruction, repair streets, plant trees and otherwise help the capital return to normal.

Radio sandino also was asking businessmen to reopen stores, movie theaters and other establishments closed and looted during the last seven weeks of civil war.

In addition to four banks that were nationalized, a fifth bank, which belonged to Somoza, was expropriated. Three U.S. banks were ordered to stop accepting deposits from the public.

Robelo told a news conference the nationalization "does not mean that we are on the way to a socialist government." He said the banks were taken over "as a social responsibility" because their assets were $100 million less than their foreign obligations.

Robelo also said the government plans to nationalize the mining, forestry and fishing industries in the future, but the economy would be a mixture of government and private enterprise.

By last night, there had been no comment from bankers in Nicaragua about the nationalization. Ernesto Fernandez, president of Banco Nicaraguense, and Eduardo Montealegre, president of Banco de America, left the country before the junta appointed by the Sandinista rebels took power. The other two banks nationalized are the Banco del Exterior and Calley Dagnal. CAPTION: Sandinista stands guard as junta meets in Managua. UPI