The United States has ordered four more members of Libya's diplomatic mission here to leave the country in apparent connection with a widespread Libyan campaign to wipe out opponents of Col. Muammar Quaddafi living in exile, a State Department spokeswoman confirmed last night.

The spokeswoman said Nuri Ahmed Swedan, Ali Ramram, Mohammed Gamudi and Abdulla Zbedi were told Friday that they have 72 hours to leave the country.

The United States is also recalling the skeleton staff at the U.S. Embassy in Tripoli.

On April 17, U.S. officials disclosed that two Libyan diplomats had been expelled from Washington earlier in the month for distributing literature calling for the "liquidation" of Qaddafi's opponents.

The four asked to leave this weekend "were engaged in activities that we consider unacceptable," the State Department spokeswoman said, and added that they were linked with Libya's campaign of intimidation against exiled opponents of Quaddafi, the Libyan leader.

Reliable sources say the four Libyans are members of a five-man committee that controls about 20 regular staff members of the Libyan mission here.

Libyan students took over the embassy here at Qaddafi's instigation in September 1979, and renamed it a "people's bureau."

The recent deaths of four Libyans, two in London and two in Rome, are widely believed to be linked to official calls for "physical elimination of the enemies of the revolution abroad." Officials, however, have not established a direct tie between the killings and the Libyan statements.

Libyan exile sources say they fear that teams dispatched by Qaddafi's agents could strike next in the United States, and informed U.S. sources say they do not discount the possiblity. One Arabic-language newspaper in London recently published what it described as "death lists" obtained from Libyan intelligence sources including 20 names of Libyans in the United States.

Qualified Americans observers say the Libyan campaign may constitute a preemptive step to check growing unrest. In recent weeks, they say, there have been reliable reports that 1,500 to 2,000 Libyans -- including senior officials in government agencies -- have been arrested. There also have been nightly show trials on Libyan television of former officials on corruption-related charges.

Last weekend, Qaddafi issued a "final warning" to dissident exiles to return home immediately in a speech to military cadets that was reported by the officials state radio.

"It is their last hope," Qaddafi said. "Either they return to Libya where they would be safe and sound or they will be liquidated wherever they are."

U.S. officials had hoped that the expulsion of the first two Libyans, Moftah S. Ibrahim, a third secretary, and Mohammed Tarhuni, a cultural attache, would be read by the Tripoli government as a strong signal that Washington is monitoring the Libyan's activities and would not tolerate any violence against dissident exiles on U.S. soil.

Nevertheless, the officials and Arab observers here note, Qaddafi is known for his unpredictability and terrorist activity in the United States could not be ruled out.

U.S. immigration and law enforcement officials are aware of the problem and are investigating possible illegal activities by Libyans students in the United States.

One of the vehicles used by pro-government Libyan students to spread Qaddafi's ideology is an Arab-language magazine called Jamahiriya, published by the North American branch of the official, government-controlled student union.

The spring 1980 issue of the magazine contains several articles -- one of them written by a student with an Arlington address -- repeating Qaddafi's call for the "physical liquidation of the enemies of the revolution aboard."

Qaddafi's calls to control the opposition come against a backdrop of growing internal discord, although analysts say there appears to be little in the way of cohesive opposition to his rule. Libya has long had discontent among its middle class and intellectuals, but observers now say there appears to be mounting dissent among the military and some of the technocrats who run Libya's oil-based economy.

With Libya's petroleum income expanding the economy and improving the standard of living, some educated Libyans tended to overlook the excesses of Qaddafi, who became known worldwide for his support of radical groups and liberation movements and is considered by many to be a Moslem zealot.

Among the prominent figurs arrested in the recent sweep in Libya have been the heads of state-run trading associations and banks, several senior customs officials and the director of Libyan Arab Airlines, Bani Hassen.

Meanwhile, the Financial Times reported from London Friday that police forces in the United States, Britain, Italy, West Germany and France have been alerted to guard against a possible wave of assassination against Qaddafi opponents. The five nations are Libya's major trading partners and have the largest Libyan communities abroad.

Libya is the source of 10 percent of U.S. oil imports and is the third-largest supplier of foreign oil to this country. Diplomatic relations between the countries have been strained, however, particularly since a Libyan mob attacked the U.S. Embassy in Tripoli last December. Since then, American representation in Libya had been reduced to a consular officer and a communicator.

The four Libyans killed recently in Europe were Mohammed Mustafa Ramadan and Mahmoud Abu Salem Nafa in London and Abdul Aref Ghalil and Mohammed Salem Rtemi in Rome. Ramaden was an outspoken anti-Qaddafi journalist and two of the other men were known to be critical of the Tripoli government.

Although U.S. diplomats hope that the expulsion of the Libyans will stave off potential attacks here, one official emphasized that "we are not out of the woods yet."

"There is no smoking gun at the moment," the official said. "But we hope there won't be."

State Department officials said earlier the two expelled diplomats were using coercive methods to control Libyan students in the United States and that their conduct was "inconsistent with the accepted role of diplomats."

Non-Libyan Arab observers here said that while Quaddafi is too unpredictable to rule out anything, it is possible that Libya primarily aims to use the intimidation campaign to control students, who potentially could be the core of an educated opposition force.

Libyan students have received notices from the poeple's bureau here to change their visa status to one that would make it more difficult to extend their stay, and those are not on government scholarships have been ordered to return to Libya or "face the consequences," according to documents made available to The Washington Post.

The people's bureau also has solicited foreign students offices at U.S. colleges and universities for the names of Libyan studants to "enable us to keep in better contact with our students."

Dissident exiles say they fear that if such information is provided, it would only make is easier for Libyan authorities -- or a "hit squad" -- to find them.