Hundreds of Tunisians chanting antigovernment slogans demonstrated this evening in apparent response to Libyan charges of Tunisian collusion in the U.S. air raid against Tripoli.

The apparently spontaneous demonstrations occurred less than an hour after Libyan radio appealed to Tunisians to rise up against President Habib Bourguiba's government which it accused of granting overflight rights to U.S. aircraft in the raid Monday.

"Cowardly regime -- accomplices of the Americans," shouted the demonstrators who were bottled up in downtown side streets by police.

The Foreign Ministry denied the charges and summoned a number of ambassadors to signal its concern about the apparent Libyan interference. Earlier, at midday, several hundred demonstrators provided the first condemnation of the U.S. air raid which the Tunisian government had been reluctant to issue.

Shouting, "American imperialists" and "Reagan assassin," the demonstrators were stopped in downtown Tunis well short of their goal, the U.S. Embassy, by truncheon-swinging riot police.

The police briefly detained about 20 demonstrators, including Ahmad Mestiri. He is the leader of the Democratic Socialist Movement, the most important of Tunisia's five opposition political parties all of which called yesterday for the government to break diplomatic relations with the United States.

Tunisia is the only Arab country that has failed to denounce the American attack on Libya. Tunis newspapers today even omitted any editorial comment or mention of the varying degrees of condemnation voiced elsewhere in the Arab world.

The official silence reflects the dilemma of a government torn between its deeply engrained suspicions of its Libyan neighbor and doubts about the tactics of its American ally.

A generation of support for the United States was broken last October when the Reagan administration initially failed to condemn the Israeli air raid on the Palestine Liberation Organization headquarters south of here.

Despite Libya's past threats and actions against Tunisia, which last September brought about a break in diplomatic relations, many Tunisians side with their fellow Arabs next door whom they see as victims of superpower vindictiveness.

Even before the Libyan radio charges, many Tunisians predicted that Qaddafi may use the David and Goliath aspects of the crisis with the United States to appeal to Arab masses over the heads of governments he considers "compromised" by their close ties to the West.

But Bourguiba is reliably reported to be opposed to criticizing the United States for fear of appearing inconsistent.