Islamic radicals again target Kuwait over jailed brethren. The imprisonment of 17 convicted terrorists in a Kuwaiti jail continues to spawn violent attempts to win their freedom. The airline hijack to Iran is the latest bid.

Tuesday's hijacking of a Kuwaiti airliner to Iran is only the latest in a series of attempts to win freedom for 17 Iranian-inspired Islamic extremists jailed for bomb attacks in Kuwait. (Hijack update, Page 32.) The attempts include the abduction of United States and French citizens by pro-Iranian Shiite radical groups in Lebanon, and an earlier hijacking to Iran of a Kuwaiti airliner in December 1984.

Three of the 17 jailed extremists - two Iraqis and a Lebanese Christian - are under sentence of death. The other 14 are serving long sentences.

All were found guilty of involvement in a spate of explosions at the United States and French Embassies, the international airport, and other targets in Kuwait on Dec. 12, 1983. Six people were killed and 80 were wounded in the blasts.

Within nine days of their conviction, the campaign to free them began.

On the morning of March 16, 1984, an official of the US Embassy in Lebanon, William Buckley, was abducted.

Buckley's captors, the clandestine, pro-Iranian Islamic Jihad organization, can hardly have believed their luck. It later emerged that he was the CIA station chief in Beirut. In the fall of 1985, the kidnap group announced his ``execution.'' US officials said he died from the effects of torture aimed at extracting the secrets of his profession.

But by the time Buckley's death was announced, the Islamic Jihad had seized five more US citizens in Beirut. It also abducted four Frenchmen during the same period.

The Islamic Jihad, which many well-placed Beirut sources say is closely linked both with Iran and with the Iranian-backed Hizbullah in Lebanon, has never spelled out publicly its terms for releasing its hostages.

But statements from the group, and from some of the hostages, make it clear a key demand is for the release of their 17 comrades.

Apart from their ideological connection as part of the Iranian-inspired regional network of mainly Shiite Muslim radicals, the kidnappers in Lebanon are believed to have a family motive for their exertions on behalf of the 17.

The man widely named as the ringleader of the Islamic Jihad's abduction operations, Imad Mughnieh, is reported to be the cousin of one of the Lebanese serving out his sentence in the Kuwaiti prison.

Three of the Islamic Jihad's US hostages were released, one by one, as part of the clandestine arms-for-hostages affair. But the group's demand for the release of the 17 convicts was not entirely forgotten by Tehran.

A Senate Intelligence Committee report published in January last year said the former national-security adviser, Rear Adm. John Poindexter, had put pressure on the Kuwaitis to free the 17, as part of the deal.

Such pressure, like the arms deliveries to Tehran, ran directly counter to Washington's declared policies.

US inconsistency over the issue - colliding with Kuwait's solidly consistent refusal to consider leniency - may be one of the main reasons the Anglican Church envoy, Terry Waite, was kidnapped in January last year, informed Beirut sources say. They say the kidnappers accused Mr. Waite of misleading them over the prospects for the 17 prisoners to be freed.

None of the four Frenchmen abducted by the Islamic Jihad in the first half of 1985 has ever been freed. One of them, researcher Michel Seurat, is believed to have died in captivity.

But there have been mounting reports since last week from both Damascus and Paris that the remaining three are to be released soon as part of a state-to-state deal involving the resumption of diplomatic relations between Iran and France.

This has prompted some speculation that the hijacking of the Kuwaiti airliner to Mashhad may have been a last-ditch effort by the Islamic Jihad or related groups to ensure that the 17 jailed militants were not once again left out of the deal.

Kuwait has consistently resisted pressure exerted by the supporters of the bombers.

In December 1984, it stood firm despite death threats to its citizens on board a Kuwaiti Airbus hijacked to Tehran by Islamic extremists seeking the release of the 17. Two US passengers were shot and killed by the hijackers.

Kuwait has been the target of numerous other acts of terrorism attributed to Iranian-inspired radicals, although it has not been clear whether they were specifically aimed at pressuring the country over the jailed radicals, or were part of a broader, Iranian-backed campaign to intimidate the Kuwaitis into dropping their support for Iraq in the Gulf war.

They include an attempt to assassinate the Emir (ruler) of Kuwait in a car bomb attack in May 1985, in which three people were killed - an action for which a number of Iraqi dissidents were convicted.

Last year also witnessed at least 10 explosions at oil facilities and other targets in Kuwait. A growing number of militants from Kuwait's own Shiite minority were among those tried and condemned for involvement in the bombings.