Repeated telephone calls were placed from a safe house in El Salvador used by Americans aiding Nicaraguan rebels to the office of a White House official who has overseen U.S. policy against Nicaragua's leftist government, according to Salvadoran phone bills.

During September, calls were made to two numbers used by Marine Lt. Col. Oliver L. North, a staff officer on President Reagan's National Security Council. According to rebel and administration sources, North has been the chief White House contact with the Contra aid network over the past two years.

An administration official, authorized to speak on the matter but insisting on anonymity, said, "To his knowledge, Colonel North has never received any phone calls from the safe houses." But another source close to North said he would not necessarily know where calls were coming from.

Another source close to the Contra aid network said the bills could have been concocted by Nicaraguan intelligence agents. But two Associated Press reporters, who have examined the documents, said they appeared to be genuine bills from Antel, the Salvadoran government's telephone company.

The calls to the White House went to two private lines that have been used in the past by North, both of which were answered yesterday by a taperecorded message saying "you have reached a non-working number for the executive office of the president."

The bills also showed calls to Stanford Technology Trading Corp. in suburban Virginia, a firm headed by retired Army Maj. Gen. Richard Secord, a former assistant deputy secretary of defense, who reportedly helped arrange aid for the Contras from Saudi Arabia.

Sccord has acknowledged giving the Contras advice, but "has steadfastly denied that he is a conduit or a middleman for Saudi Arabian aid," said his lawyer Tom Green.

Another number listed on the bills belonged to Southern Air Transport Inc. of Miami, a onetime CIA-owned company which had employed one of two American pilots killed when a C-123 cargo plane was shot down over southern Nicaragua on October 5.

A third American, Eugene Hasenfus, was captured, and said the air supply operation, which included dropping weapons and ammunition to Contra forces inside Nicaragua, was directed by two Cuban-Americans who worked for the CIA. The CIA, the Reagan administration and Southern Air have denied responsibility for the supply operation.

From October 1984 until this month, U.S. government military assistance to the Contras would have been illegal, but two weeks ago, Congress approved resumption of direct U.S. military aid to the rebels.

The AP has previously reported that the White House, through outside intermediaries, managed the aid network that was established in 1984 to keep the Contras supplied, using funds from private individuals and third countries. Sources from inside the administration, the Contra movement and the private aid network identified North as the central figure in the secret White House operation.

Other documents captured by the Nicaraguan military from the downed C-123 also linked the U.S. government to the plane's occupants.