Gunmen in Chile assassinated a retired Army general serving as governor of Santiago this morning, and Chilean Interior Minister Sergio Jarpa said the attack was "calculated to cause the failure of the political liberalization" of the government of Gen. Augusto Pinochet.

Retired major general Carol Urzua, Santiago's chief administrative official, was killed with his driver and his bodyguard when the car they were riding in was hit by a burst of machine-gun fire on a street in east Santiago, Chilean authorities said. It was the most serious attack on a member of the ruling armed forces since l977.

There had been no arrests in the case by late today.

The Associated Press reported from Santiago that a previously unknown group calling itself Guerrilla Militias and Forces of Popular Revolution claimed responsibility for the killings. The group's statement was written on stationery of The Revolutionary Movement of the Left, a group that was virtually wiped out by security forces after Pinochet came to power in 1973.

In Washington, State Department spokesman John Hughes said the killing "should not be allowed to impede continued progress toward the peaceful resolution of political differences in Chile or to obscure the recent positive moves taken by the government of Chile to restore important political and civil liberties," AP reported.

The assassination came amid a major effort by the Pinochet government to reach an agreement with a national opposition movement and nine days before the beginning of scheduled antigovernment demonstrations on the 10th anniversary of the coup that brought the military to power.

Jarpa, who has led recent government moves to permit return of political exiles, legalize political activity and move up legislative elections, said in a meeting with reporters here in Buenos Aires that he believed the assassination was the work of leftist terrorists. He dismissed speculation that military or rightist elements opposing the new political program could have been responsible.

"It is very significant that it the killing happens at this moment," said Jarpa, who was named interior minister Aug. 10 and is in Argentina to take leave of his previous post as ambassador to Argentina. "It is a criminal act meant to undermine the current government policies."

He said he did not believe the government would take exceptional measures in response to the assassination and that the state of emergency lifted in Chile two days ago by Pinochet would not be reimposed.

In Santiago, political and diplomatic sources contacted by telephone said the slaying appeared to be viewed by government and military authorities as an isolated incident that would not lead to a larger political crisis.

Urzua, 57, had served as governor of Santiago since December 1980 and was considered close to Pinochet.

Jarpa, a former president of the conservative National Party, said here today that the government intends to end four months of growing antigovernment protests by "channeling opposition activity into a normal system."

He said that the government would soon begin consideration of a new statute legalizing Chile's currently banned political parties and that party activity could legally begin by early next year.

Opposition leaders have met with Jarpa this month to discuss government political liberalization, but they have remained firm in their plans for a fifth consecutive monthly national protest against Pinochet next week.