Shops reopened in Tripoli and airline flights resumed yesterday as Libya began returning to normal four days after it was attacked by U.S. warplanes in an effort to discourage terrorism allegedly sponsored by Libyan leader Muammar Qaddafi.

State television showed footage of Qaddafi visiting graves of the air raid victims and receiving the defense ministers of Burkina Faso and neighboring Sudan.

But the repercussions from the largest U.S. Air Force strike since the Vietnam War continued: Three passports believed to be forged were found in a jumbo jet's lavatory during a stop in Cairo, raising fears that terrorists might have been aboard; a bomb in Istanbul was defused outside a bank with U.S. connections, and anti-American protests raged in cities around the world, according to news agencies and correspondents' reports.

A TWA Boeing 747 en route to New York from Bombay was delayed in Cairo for four hours yesterday after a flight attendant found three passports in a toilet. The passports contained no photographs but had visas for the United States and West Germany, officials said.

Airport officials said the passports, found as part of tighter security precautions, were issued by Bahrain to persons not listed as passengers on the flight. Officials speculated that they may have been tossed in the lavatory by terrorists or criminals who learned that they would be searched during a stopover in Cairo. The 122 passengers on board were searched before the flight was allowed to proceed.

In Istanbul, Interior Minister Yildirim Akbulut said a bomb was found at the entrance of the Koc-American Bank and defused safely yesterday.

U.S. Embassy spokesman David Arnett said that Americans were being warned "to take extra precautions and not be going out unnecessarily," news agencies reported from Ankara.

On Friday, Turkish police arrested two Libyans who were carrying a bag filled with hand grenades and other explosives outside a U.S. military officers' club in Ankara. Two other Libyans were arrested later, apparently on information from the first two, the semiofficial Anatolian News Agency reported.

The evacuation of Americans from Sudan as a precaution against terrorist attack continued last night with the departure of 124 persons, including 30 children, aboard a chartered Swiss Air jet.

A U.S. Embassy official in Khartoum said most of the evacuees were Americans and their families who had been working in Sudan for U.S.-based famine relief agencies. In the past two days, 298 persons, almost all of them U.S. citizens, have been evacuated to Nairobi, Kenya.

In London, about 10,000 people demonstrated outside the U.S. Embassy against the raid on Libya and hundreds marched on Prime Minister Margaret Thatcher's residence at 10 Downing St. to protest her government's decision to allow U.S. planes to launch their attack from bases in Britain.

"Reagan, the world's worst terrorist" and "Thatcher, traitor," said placards carried by the demonstrators.

Thousands of demonstrators shouting "Hands off Libya" and "U.S. genocide" marched to the U.S. Embassy in Bonn, Reuter reported.

Similar incidents were reported in Argentina, the Philippines and the Dominican Republic. In Vienna, 4,000 demonstrators burned an effigy of President Reagan as 500 Austrian police guarded the U.S. Embassy. In Rome, demonstrators condemned both Reagan and Qaddafi.

Bomb threats in Toronto and Montreal delayed the departure of an Air France flight bound for Paris and Delta Airlines flights for Miami and Boston.

In London, police said an Irish woman who was arrested as she tried to board an El Al airliner at Heathrow Airport Thursday with a bomb in her luggage was released yesterday. No charges were filed against her.

Antiterrorist detectives questioned the woman's boyfriend, Nezar Hindawi, suspected of trying to blow up the jetliner. Police said that they believed the woman, Anne-Marie Murphy, was duped by Hindawi, a Palestinian.

In Dublin, Danny Morrison, national director of Sinn Fein, the legal political wing of the outlawed Irish Republican Army, extended sympathy to Qaddafi and pledged Irish nationalism's solidarity with Libya, according to The Associated Press. Qaddafi reportedly has contributed funds to the IRA in its fight to oust Britain from Northern Ireland.

Tunisian President Habib Bourguiba called in the U.S., French and Algerian ambassadors in an apparent bid to show support from Tunisia's three major protectors in the face of possible Libyan subversion. Tunisia is the only Arab country to have remained silent after the U.S. air raids against Libya.

Libya's foreign minister, Kamal Hassan Mansour, told foreign ministers of the Nonaligned Movement meeting in New Delhi that U.S. policies threatened peace and called for struggle "against the U.S.A. and its hegemony," news agencies reported.

Authorities in Athens broke up a news conference by Libyan Deputy Foreign Minister Ahmed Shahati after he contradicted a Greek statement that he had asked for European Community mediation in resolving the U.S.-Libyan confrontation.

Police ordered reporters to leave the press conference and said they were acting on instructions of a government minister. Greek officials later said the press confrence had been stopped for security reasons.

Libyan officials in Tripoli said that a bomb that did not explode during the air strike Tuesday blew up in a residential neighborhood last night, injuring three persons, but there was no independent confirmation of the report.