MANAGUA, SEPT. 12 -- Msgr. Bismarck Carballo, exiled last year by the Sandinista government, returned to his country tonight from the United States and went directly to celebrate a mass in his former Managua parish.

"One of the rights I was deprived of has been restored. I'm back in my homeland," Carballo said as he stepped onto the tarmac at Sandino International Airport, where about 1,000 cheering supporters greeted him with drums and firecrackers.

President Daniel Ortega announced Aug. 25 that Carballo would be allowed to return home as a gesture of good faith under a regional peace plan signed Aug. 7 in Guatemala by five Central American presidents. But Roman Catholic and political opposition leaders were reluctant to view his homecoming as an advance toward the full democracy promised in the accord.

"This action makes many of our faithful happy. But peace is not made of this alone. We hope to see concrete measures," said Nicaragua's Roman Catholic leader, Cardinal Miguel Obando y Bravo. The cardinal returned with Carballo from Miami, where he accompanied Pope John Paul II but did not, he said, get to meet with the pontiff.

"This is no step forward. This is simply the government's recognition of a past injustice," said Erick Ramirez, president of the Social Christian party, the largest opposition group.

Carballo, a government critic, was head of the Catholic Radio and Obando's chief spokesman when his return from a visit to the United States was blocked June 28, 1986 -- two days after the House of Representatives approved $100 million aid for the rebels known as contras.

Carballo said he hoped the radio, off the air since January 1986, will reopen shortly, but he has no assurances. While in exile, Carballo served in a rural Maryland parish.

Returning with him was an Italian missionary, Father Benito Pititto, expelled in July 1984 along with nine other priests. Pititto, who served 25 years in Nicaraguan parishes before he was banned, said he never lost hope that he would be allowed to come back.

Nicaraguan Bishop Pablo Vega, the third clergyman permitted by Ortega to come home, has not accepted the offer. A vociferous adversary of the Sandinista government, Vega has said he fears for his life if he returns.