Sudanese rebels, taking advantage of a general strike that has paralyzed the nation's capital and cut it off from the outside world since Wednesday, said today that they have established secret contacts with officers of the Sudanese Army.

The meetings, announced over the radio of the Sudanese People's Liberation Army, were said to be in response to a call by rebel leader John Garang for direct talks with the Army, excluding President Jaafar Nimeri.

There was no independent confirmation of the rebel claims, and no further details were given. But Garang, a former Sudanese Army colonel, was making his appeal to an increasingly embattled institution.

Despite deep religious differences, both the professionals' unions striking in the Moslem north and the Christian and animist rebels fighting in the south are now clearly intent on bringing Nimeri's 16-year rule to an end.

The armed forces repeatedly have found themselves caught between these groups and the increasingly unpopular president, whose nation is in serious economic trouble and whose rule has been characterized by a long series of erratic political alliances and reversals.

Nimeri, an important ally of the United States, has been visiting Washington since last week.

He left the United States this afternoon.

The immediate cause of the protests are a devaluation of Sudanese currency and an end to many subsidies on basic goods, decreed by Nimeri under pressure from the International Monetary Fund and the Reagan administration.

[Sudan's state-run radio resumed transmission Friday, United Press International reported, broadcasting accusations that Libya was behind the current unrest.]

Communications with Khartoum, the capital, remained spotty today, with commercial telex and telephone lines shut down and the airport closed. News agencies, citing diplomatic sources, reported the city calm despite the strike.

But accounts brought out by passengers on the last commercial flight to leave Khartoum yesterday morning suggested more tension in the streets than had been reported previously.

According to these travelers, who asked not to be quoted by name, Newsweek photographer Anna Clopet and other journalists were beaten by baton-wielding riot police while photographing demonstrations Wednesday.

The British Embassy told the Newsweek correspondent here that Clopet was struck on the head and throat with rifle butts.

Clopet is now reported safe and in close contact with the British Embassy.

Other photographers reported that their film and videotapes were confiscated, although most police units were described as restrained and reluctant to enter violent confrontations with the crowds.

Egyptian officials have been guarded in their statements but clearly view the situation with serious concern. Because Sudan controls the upper reaches of the Nile River, the nation is considered vital to Egyptian security.

In an interview published yesterday, Egyptian President Hosni Mubarak said that what is happening now in Sudan appears to be an internal matter. But in a warning aparently directed at Libya, Mubarak said that "if Sudan were subjected to an external menace, then we will be with it at once."