Aides of Sen. George McGovern (D-S.D.) charged today that Rhodesian security police broke into the hotel rooms of the senator and other members of his party during their three-day stay in Rhodesia.

Pauline Baker, counsel for the Senate Foreign Relations subcommittee on Africa, said the rooms were entered Monday night, papers were rifled through and locked briefcases were broken into. Nothing of value was taken, Baker said.

The Rhodesian Foreign Ministry today denied any knowledge of the incident or that Rhodesian police were involved.

McGovern lodged a formal complaint with the Rhodesian government over the break-in but the complaint did not specifically mention the security police. The senator, who flew to South Africa today, was unavailable for comment.

Baker said the McGovern party, which includes a State Department liaison officer, was highly suspicious that the security rorces carried out the operation since the Rhodesian government had posted a guard on the floor of the Meikles Hotel where the senator and his aides were staying. Presumably the guard would have had to know about anybody entering the rooms.

McGovern left here expressing pessimism about the success of the elections Rhodesia is planning to hold next April for a black majority government. "The big question," he told reporters at the airport, "is whether that can be carried out without continued slaughter between blacks."

During his stay here, McGovern met with Prime Minister Ian Smith and the three black members of Rhodesia's ruling Executive Council, visited the training center of the Selous Scouts, the Rhodesian Army's equivalent of the American Green Berets, and met a former nationalist guerrilla leader now supporting the Smith-led government.

McGovern's trip, which so far has included stops in Sudan, Tanzania, Mozambique and Rhodesia, is thought to be in preparation for his possible takeover of the Africa subcommittee of the Senate Foreign Relations Committee chaired by Sen. Dick Clark (D-Iowa), who was defeated in the November election.