Leftist guerrillas fired mortars at the home of U.S. Ambassador Alexander Watson, and one round struck the roof, causing minor damage but no injuries, U.S. Embassy and police officials said.

Embassy spokesman Joao Ecsodi said Watson, his wife and their infant daughter were in the two-story, colonial-style residence and heard one mortar round strike the roof."The ambassador thought at first it was the backfire of a car. It was not a big explosion," Ecsodi said.

He said the 60mm mortar round destroyed a ramp and lighting fixture on the roof. Ecsodi said there was no other damage.

Police said at least three rebels fired three rounds at the residence, but Ecsodi said the embassy was aware of only two mortar rounds.

Members of the pro-Cuba Tupac Amaru Revolutionary Movement left fliers where the mortars were launched, about one block from the residence, Ecsodi said.

The fliers commemorated the death of a pro-Cuba guerrilla leader, Luis de la Puente, who launched his insurgency on June 9, 1965. He was killed in combat four months later and his group broken up. The Tupac Amaru band became active in 1984.

The building is enclosed behind a 10-foot-high concrete wall. The building and gardens cover nearly a square block.

Ecsodi said Watson was having breakfast when the attack occurred at 6:30 a.m. (:30 a.m. EDT).

Embassy officials did not say what happened with the other mortar rounds, which apparently missed their target.

In April 1986 the Tupac Amaru rebels exploded a car containing 130 pounds of dynamite at the side of the rear wall enclosing the compound. The explosion damaged the wall but cause no damage to residence.

The ambassador then was David Jordan. Watson has held the post since late 1986.