Iraqi jet hijack bears mark of pro-Iran radical Muslims. But Iraqis' swift action hides terrorists' identities, demands.

Like other recent acts of terrorist violence in the Middle East, the Christmas Day hijacking of an Iraqi airliner has left a trail of unanswered questions. But most of the signs were that, whatever their nationality, the hijackers were pro-Iranian Muslim extremists. If so, this would be the first attempted hijack attributed to such people since the TWA hijacking to Beirut in June 1985.

According to the Iraqi News Agency, 67 of the 106 passengers and crew on board were killed when the damaged Boeing 737 crashed landed in the desert a half mile from Arar airfield in northern Saudi Arabia Dec. 25.

Armed Iraqi security men had tackled the terrorists as soon as they tried to hijack the plane, about an hour after it left Baghdad, Iraq, on a scheduled flight to Amman, Jordan. In the battle, a grenade exploded in the cockpit and another in the rear of the aircraft, forcing the pilot to divert and make a crash landing.

The small number of survivors able to describe what happened was one of several reasons why so little has emerged to explain the incident. Another was that the investigations by Saudi, Iraqi, and other Arab authorities have been shrouded in secrecy. And because the swift intervention of Iraqi sky marshals kept the incident from developing into a full-fledged hijacking, the terrorists' demands and affiliations remained unknown.

According to survivors, there were four would-be hijackers. Two were killed in the gun battle and the crash. One was wounded and another unharmed. Both were arrested by Saudi authorities, who have said nothing. Survivors and Iraqi officials said the gunmen were traveling on Lebanese passports - which does necessarily mean they were Lebanese nationals. The official Iraqi version described the men as ``Iranian agents'' - which does not necessarily mean they were Iranian nationals.

The situation was further confused by a rash of responsibility claims issued in Beirut in the name of a number of clandestine groups, most of them hitherto unknown. They included the Revolutionary Action Organization, the Shiite Revolutionary Organization, the Revolutionary Islamic Movement, and the Islamic Jihad. Of these, only the Islamic Jihad had been heard of before.

However, a statement from the Islamic Jihad cell which is known to be holding at least two American hostages denied having any involvement in last week's hijacking incident. The statement was delivered to an international news agency in Beirut yesterday.

Given the informal and clandestine nature of such groups, the four responsibility claims lodged in Beirut were not necessarily incompatible. In any case, the names used for the three claims by unknown groups all indicated that they, like the Jihad, are pro-Iranian fundamentalist (and probably Shiite) Islamic extremists - as the target for the operation also strongly suggests.

Iraq itself lost no time in accusing Iran for the incident. But the Iranian Foreign Ministry immediately issued a denial of any involvement, adding: ``We condemn any actions that might threaten the lives of innocent passengers.'' Iran held this official position in previous hijackings that did involve pro-Iranian extremists.

Official Iranian denials did not dissuade US officials from publicly expressing suspicions that at least a faction within the Iranian power system was involved in sponsoring such actions, by activating allied groups of Shiite revolutionaries abroad.

Assuming, as most observers in the region have done, that last week's hijacking was the work of a pro-Iranian extremist faction - such as the Iranian-backed dissident Iraqi fundamentalist group called al-Dawa al-Islamia (``Islamic call'') Party - why should the group suddenly revive such actions after a hiatus of more than 18 months?

Analysts say that, whether they belonged to al-Dawa or another Iranian-inspired underground group, the hijackers might have been acting independently of Iran, perhaps hoping to obtain the release of comrades imprisoned in Baghdad.

But, they add, if the hijackers were activated by a faction in Iran itself, as has been suspected in past cases, the affair might be linked to the muted power struggle within the Iranian regime that has been reported in recent months.

The man who was in charge of Iran's relations with Islamic revolutionary groups abroad during the earlier hijackings, Mehdi Hashemi, has been disgraced and arrested in what most observers have seen as part of that struggle. After his arrest in early October, his followers are widely believed to have been responsible for exposing Tehran's secret dealings with the US.

Mr. Hashemi's revolutionary movement is fiercely opposed to such contacts with the US, which are believed to have had the discreet support of the powerful speaker of Iran's parliament, Hojatolislam Hashemi Rafsanjani. Despite the revelations, Mr. Rafsanjani is reported to have emerged stronger than ever, because of the suppression of Mehdi Hashemi and other extremists. Rafsanjani and other mainstream leaders in Tehran have openly offered to resume arms dealing with Washington.

If there was indeed an Iranian connection with last week's hijacking, some analysts say it may have been inspired by revolutionary radicals with the aim of preempting any such resumption of a US-Iran dialogue.