The four terrorists who hijacked the Lufthansa jetliner Oct. 13 remains officially unidentified but foreign diplomatic sources here disclosed today that three of them possessed Iranian passports while the fourth was travelling on a Dutch passport.

It was not revealed however, whether these travel documents were forged or stolen and the Somali government continued to maintain strict secrecy surrounding its investigation, not permitting anyone to visit the sole surviving terrorist.

The survivor, identified as Shahnaz Gholam, 22, is being kept under heavy guard at Mogadishu's Medina hospital with slight gunshot wounds in her shoulder and leg. She was captured while shouting in Arabic to bystanders following the spectacular West german commando raid here in which her three colleagues were killed early last Tuesday morning.

During the five-day hijacking odyssey, the four hijackers were heard to communicate in Arabic and in broken English. Since neither Iranians nor Dutch normally speak Arabic, some diplomats here sceptical about the authenticity of the passports.

A well-informed Arab dipomat here said however, that he knew that the passports were genuine and that none of the hijackers was Arab. A Chinese doctor who saw the bodies reportedly suggested that the three slain terrorists were all rather fair colored, looking more European than Arab. Some sources suggested that the surviving girl was a Palestinian.

The Somalis have clamped complete secrecy on their investigation of the incident, presumably fearing the wrath of radical Arab and African leftists for permitting West Germans to mount a military assault on the leftish hijackers at Mogadishu airport.

Some Arabs sources here suggested that the terrorists may have been associated with am extreme Palestinian group, the so-called Popular Organization led Wadhir Hadded. Hadded had dropped out of sight after he was expelled two years ago from the leadership of another radical Palestinian group, the Popular Front for the Liberation of Palestine.

Although the front is regarded as one of the most radical Palestinian groups. Hadded is expulsion from its leadership was reported to have been based on charges that he had been too radical.

The consensus here is that the hijackers were part of an international terrorist network that embraces offshoots of the West German Baader-Meinhof gang, the Japanese Red Army, and allies of Carlos, the Venezuelan terrorists operative.

According to the passports, the dead hijackers were Jojannes Gerdus, a Dutch citizen, and Reza Abassy and Soraya Ansary, both Iranian nationals.

Gerdus, who was believed to have been the spokesman for the group had identified himself during the hijacking as Walter Mahmoud.

The surviving woman, Gholam, was wearing a Che Guevara t-shirt and was shouting "Palestine will live " in Arabic when she was captured. She also shouted abuses at the Somalis and gave a V-for-victory sign. "The Somalis are not true Moslems," she said.

The three terrorists who died in the west German asyault early last Tuesday that freed 86 hostages reportedly have been buried here.

Just how the investigation is being conducted and who else is involved apart from the Somalis has not been revealed. There are reports that West German police and Interpol are involved, but the degree of their involvement and Somalis's cooperation with outside investigators could not be discovered.