Intercepted coded messages to Fidel Castro's Africa corps in Angola "covering a period of several days" before the invasion of Zaire's Shaba province make up part of the evidence to support President Carter's charge of Cuban complicity in the invasion.

In addition, the CIA has possession of "human intelligence" reports - possibly from Cuba, possibly from Angolan sources - that corroborate the intercepts.

That background explains Carter's cold anger in totally disregarding Castro's personal protestation of innocence in a Carter-Castro confrontation that may have wide-ranging international impact.

Challenged by Sen. George McGovern (D-S.D.) to prove his accusation against Castro, Carter ordered CIA Director Stansfield Turner to begin testimony on Capitol Hill before the Senate and House Intelligence committees, probably next week.

Turner labors under a heavy burden of responsibility to protect American intelligence agents and sources. A leak from a member of Congress could destroy sources and costs lives.

The necessity for protecting sources, then, could leave the president open to renewed challenges from McGovern and other congressmen: Supply proof positive that Castro was lying when he denied any Cuban role. That does not disturb Carter. He is certain that Congress will take his word over Castro's or Soviet Foreign Minister Andrei Gromyko, who infuriated the president with his May 27 statement on the White House lawn that Carter's information was faulty.

Indeed, evidence now being collected to prove the complicity of Moscow. Havana and other Soviet satellites in the murderous rampage of the Angola-based Shaba invasion force leaves no possibility of doubt. A central element has been Soviet use of communist East Germany.

In his hard-hitting "Meet the Press" appearance on May 28, Zbigniew Brzezinski fingered the East Germany as a chieobliquely. In fact, the record of East germany as a chief Soviet agent in Africa is just now becoming clear.

Moscow assigned East Germany the principal communist coordinating role for intelligence and "security matters" in Ethiopia, Mozambique, Angola and several others states targeted by the Soviet Union. A special secretariat to handle that task, and oversee supplies of arms, was created in the early 1970s under East Germany's deputy foreign trade minister. In those Soviet-targeted countries, East Germany is credited with having more on-the-scene agents than any country except the Soviet Union itself.

Special targets are the "liberation" armies now poised outside Rhodesia's frontiers under Robert Mugabe and Joshua Nkomo and the "National Peoples' Armies" of Angola, Ethiopia and Mozambique.

Early this month, in a speech in Addis Adaba, Lt. Col. Haile-Mariam Mengistu, the Ethiopian strongman, boasted that "progressive comrades" from East Germany "live with us, fight with us and die with us." When the speech was broadcast later in English, that phrase was deleted. One year earlier, a Western European intelligence service reported the capture of three East German soldiers in the Zairian town of Mutshatsha during the first (1977) Angola-based incursion into Zaire.

With such a wealth of evidence at his disposal, Carter's charge of non-African communist complicity in the 1978 invasion of Zaire is beyond dispute. But adding to the White House use of harsh rhetoric is the president's anger at the Cuban denials that led McGovern to demand that te president, in effect, "prove it."

Carter was made to look ridiculous when he volunteered on Feb. 16, 1977, that he had received "information from indirect sources" that Castro had "promised" to remove his Africa corps (then numbering about 15,000 from Angola. Instead of withdrawal, the force has been increased.

That was a repeat of history. Henry Kissinger, as secretary of state, informed the world on May 26, 1976, that Castro had told then - Swedish Prime Minister Olaf Palme in a letter that he would withdraw 200 Cubans a week from Angola. The letter indicated that Castro would send no Cuban troops elsewhere in Africa, adding, "I do not wish to become the crusader of the 20th century."

In May 1977 Castro told interviewer Barbara Walters he would send neither advisers nor troops to Ethiopia, where today some 17,000 Cuban troops are in residence.

Against that record, Carter, and Brzezinski were not impressed on May 18 when Castro summoned U.S. diplomat Lyle F. Lane in Havana to deny any Cuban role in the invasion of Zaire. Castro's words is not highly regarded in the White House.

How the CIA will handle the evidence in supposedly confidential briefings on Capitol Hill is not yet known. Nor can it yet be known where the bold rhetoric from the White House about communist marauders in Africa will finally lead. What is clear is one fact: Jimmy Carter knows he has been lied to.