Arabic-speaking hijackers Tuesday commandeered a Kuwaiti Airways jumbo jet with 111 people aboard including four members of the Kuwaiti royal family forced it to land in Iran and threatened to blow it up.

Kuwait urged Iran to handle the incident "wisely" and asked that the Boeing 747, which was hijacked on a flight from Bangkok to Kuwait, not be allowed to take off from Mashhad airport in northeastern Iran.Iran first denied the plane permission to land but reversed its decision when the pilot said the jet was running out of fuel, said Iran's Islamic Republic News Agency.

It was not known what the hijackers' demands were. Relations between Iran and Kuwait have been strained by diplomatic disputes and the Persian Gulf war.

Prime Minister Hussein Musavi of Iran told Tehran Radio he was trying to "resolve the incident peacefully to save the lives of the people on board."

He sent his deputy for political affairs, Ali Reza Moayyeri, to Mashhad to "look into the hijack situation," said the broadcast, monitored in Nicosia.

Kuwaiti Airways, Kuwait's only flag carrier, said Flight 422 from the Thai capital was carrying 96 passengers and 15 crew members.

The Foreign Office in London said the travelers included 22 Britons. Airport sources in Bangkok said other passengers included at least one Japanese and about eight Thais. There were no reports of any Americans aboard.

IRNA, also monitored in Nicosia, had reported that the flight originated in Kuwait. But Kuwaiti Airways offices in Kuwait and Bangkok said the plane took off from Bangkok.

IRNA said the aircraft landed in Mashhad at 7:30 a.m. (midnight EST) and completed refueling three hours later.

It said the aircraft was "preparing to fly to an unidentified destination." But several hours later, there still was no word that the jet had taken off.

IRNA said that while demanding fuel, the hijackers threatened to blow up the aircraft if "any person should attempt to approach it."

The Iranian agency said the hijackers spoke in Arabic but did not identify themselves or make any demands. IRNA did not say how many hijackers were aboard the plane.

The Kuwait News Agency quoted a spokesman for the airline as saying contact was lost with the aircraft while it flew over Muscat, Oman.

An Iranian Foreign Ministry spokesman said the plane flew into Iranian airspace from the direction of the Gulf of Oman.

He told IRNA that initially, the aircraft was refused permission to land in Iran but that the pilot radioed back saying he was running out of fuel.

"The Kuwaiti plane was allowed to land at the airport solely for humanitarian reasons," the unidentified spokesman was quoted as saying.

He said: "The Islamic Republic of Iran as a rule condemns hijacking and any similar act which might threat the lives of innocent people."

Musavi, the Iranian prime minister, said hijackings were "against humanitarian and Islamic principles and unacceptable as a political tactic."

In Kuwait, a government spokesman said the Foreign Ministry summoned Iranian Charge d'Affaires Mohammed Faroughy

and told him "Kuwait is confident that the concerned Iranian authorities will handle the issue wisely, in a manner that ensures the safety of the passengers, the crew and the plane."

The unidentified Kuwaiti government spokesman told the Kuwait News Agency, "Kuwait also asked the Iranian government not to allow the airliner to take off from Iran and to take all measures necessary to prevent such takeoff."

The Kuwaiti spokesman described the hijacking as a "regrettable incident" but gave no indication as to who may have been behind it.

Diplomatic relations between Iran and Kuwait have been strained since August when Iranians stormed the embassies of Kuwait and Saudi Arabia in Tehran. Kuwait closed its embassy in Tehran and brought its diplomats home. Later Kuwait limited the number of Iranians at Iran's Embassy in Kuwait to two.

Pro-Iranian gunmen hijacked a Kuwaiti Airways jetliner to Tehran in December 1984. They killed two American passengers, Charles Hegna, 50, and William Stanford, 52, before Iranian commandos stormed the aircraft, ending the six-day ordeal.

At the time, the hijackers demanded the release of Kuwaitis jailed in the 1983 bombings that targeted U.S. and French embassies in Kuwait. The Kuwait government refused to negotiate.

Dozens of Shiite Moslem terrorists, most of them either of Iranian descent or loyal to its Islamic Revolution, have been arrested and convicted of sabotage in the past five years. The overwhelming majority of Iran's population is Shiite.

In the Persian Gulf Arab states, Sunni Moslems dominate the government.

Kuwait is the closest Arab nation to Iran and Iraq, which are locked in a 71/2-year-old war. Iran has often accused Kuwait of actively aiding Iraq's military effort.