The emir of Kuwait narrowly escaped assassination today as a suicide bomber drove a car into his motorcade in an attack apparently linked to efforts by Islamic extremists to force the release of 17 prisoners held by the Kuwaiti government.

The emir, Sheik Jabir Ahmed Sabah, 59, was reported by Radio Kuwait to have suffered only minor cuts from flying glass and was released from the hospital after four hours, but at least four persons, including the driver of the car, were killed in the attack along the Kuwait City waterfront at 9:15 a.m. The group calling itself Islamic Jihad claimed responsibility for the assassination attempt.

It was unclear whether the suicide vehicle was in the motorcade at the time of the blast, but bystanders were quoted as saying it sped out of a nearby gas station, crashed into the motorcade near Sabah's limousine and exploded.

Telephone calls to news agencies in Beirut repeated demands for release of the prisoners held in Kuwait for a string of bombings there in December 1983, including attacks on the French and U.S. embassies, that killed six persons and left more than 80 injured. "We once more demand the release of the detainees," a caller told Reuter. "Otherwise all the thrones in the gulf will be shaken."

"We hope his royal highness has received the message," the caller said. Similar anonymous calls last week warned that failure to release the Kuwaiti prisoners would have "catastrophic" consequences for four American and two French hostages kidnaped in Lebanon during the past two years. Kuwait has rejected the demands.

Kuwait closed the country's borders to foreigners in what was called a temporary security measure as an intensive hunt began for possible accomplices in the assassination attempt, Reuter reported.

In an earlier statement, Kuwait's crown prince, Sheik Saad Abdullah, said his government will "not submit to threats or blackmail."

With bruises and treated cuts visible on his face, the emir went on radio and television four hours after the explosion and told his 1.6 million subjects he was unharmed, The Associated Press reported from Kuwait.

"I wish to assure you, citizens, that I am in good health," said the emir in a firm voice. His head was covered with the traditional scarf, minus the usual black cord.

"The incidents to which we are subjected will not distract us from proceeding on with our policy of cultivating prosperity for this nation, Arab and Islamic peoples," he said.

Noting that several persons were killed, including the emir's driver and at least one bystander, a State Department spokeswoman said, "We deplore this loss of innocent life and have conveyed our sympathy to the government of Kuwait. We support the strong stand against terrorism and violence taken by the Kuwaiti government."

The demands of the anonymous callers in Beirut appear to tie today's bombing in Kuwait to a complex underground of Shiite fundamentalists who are best known for their Lebanese factions but who also represent a significant political element in the 56-month-old Iraqi-Iranian war.

Iraq blamed Iran for the attempt on the emir's life and said it would raid targets in Tehran in reprisal.

Iraqi warplanes attacked central Tehran early Sunday, breaking a six-week lull in the gulf conflict, Agence France-Presse reported from Tehran. One person was reported killed and six were injured. The Iranian High Defense Council, in a statement carried by Tehran radio, warned to turn the Iraqi capital "into hell" in reprisal, AFP reported.

Saudi Arabia, Kuwait and the other, smaller states along the Persian Gulf that support Iraq are considered by diplomats to be vulnerable targets for direct attack or internal subversion by Iran in the protracted conflict. The possibility of a widened war drastically affecting world oil supplies is a constant concern of the United States, which has been accused of tilting toward Iraq in the past three years despite official neutrality.

Iraq has warned recently that when Iran's large frontal offensives against Iraq are frustrated, it resorts to measures against weaker targets. The 17 prisoners in Kuwait have become central figures in the chess game. The prisoners reportedly are members of the Shiite group known as Al Dawa ("The Call"), which advocates the replacement of Saddam Hussein's 17-year-old secular rule by an Iranian-style, Shiite-dominated theocracy. It was Iranian backing for such groups here that led to the current war, Iraqi officials insist.

An Iraqi official cited several apparently related incidents: the Kuwait bombings in 1983, the hijacking of a Kuwaiti airliner to Iran last December that ended after two Americans on board were killed and two others beaten in an effort to force the release of the 17 prisoners, a mysterious bombing in Saudi Arabia earlier this month and today's attack in Kuwait.