Nearly four weeks after he was last seen scrambling into an armored personnel carrier at the start of South Yemen's bitter fighting, mystery continues to surround the whereabouts of the ruling Socialist Party's leading Marxist ideologue, former president Abdul Fatah Ismail.

Ismail's popularity within the party has soared during his absence, already turning him into a legendary figure who -- if he is still alive and manages to surface -- could influence the political direction of this strategic, Soviet-supported desert nation.

His photograph can be seen on storefronts and car windshields in the capital and the provinces, and members of the party frequently invoke his name, less as a martyr than as a living hero. They hope that -- as he had once done after spending five years in exile in Moscow -- he will return victoriously to take the reins of leadership and steer South Yemen's socialist experiment further toward Soviet-style Marxism-Leninism than did deposed president Ali Nasser Mohammed or his successor, Haidar Abu Bakr Attas.

[South Yemen's former deputy prime minister and fisheries minister, Yasseen Said Noman, was sworn in Saturday as the new prime minister, Reuter reported. Noman succeeded Attas, named head of state in place of the ousted Nasser Mohammed.]

Attas' government appears undecided about what to say about Ismail's fate after he escaped a massacre Jan. 13 at the party's secretariat. A leading member of South Yemen's Politburo said an announcement would be made soon about his whereabouts, based on the findings of an investigation.

"We hope that he is alive. The committee is investigating the destiny of this car and we will report soon," said fellow Politburo member Salem Saleh Mohammed.

Many South Yemenis take such bland statements with a grain of salt, and assume that Ismail is alive and is either waiting for an opportune time to make a bid for power or is being kept behind the scenes because of his advocacy of radical social and political measures that could impede efforts to improve relations with North Yemen, Saudi Arabia and Oman.

Ismail was rumored to have been gravely wounded during the fighting around the secretariat on Jan. 13 when Nasser Mohammed's gunmen tried to eliminate the then-president's political opponents in a bloody preemptive strike, killing three of the six Politburo members whose criticism of him had become increasingly open.

Ismail was one of the three who retreated from a bullet-riddled conference room to a ground-floor office in the secretariat and then hid there under fire for seven hours while they appealed by telephone for loyal Army troops to rescue them.

Armored vehicles arrived, and Ismail, according to one of the three surviving Politburo members, Ali Salem Baid, was last seen leaving in one of them as it came under fire.

Baid, who later was wounded in the thigh and the abdomen, said that he did not know what became of his Politburo colleagues because they escaped in separate vehicles. Ismail's home was gutted by a fire started by tank shelling, but party officials said that neither he nor his family were in the house at the time and that no bodies were found.

Party leaders have been vague about Ismail's fate, being careful not to lead reporters to the conclusion that he was killed, and at the same time leaving the impression through their repeated assurances of a full report in the near future that they know his whereabouts but are simply not disclosing it.

Saleh, in a discussion about Ismail, repeatedly referred to him in the present tense, saying at one point, "He is a great, militant leader, a thinker, so it is not strange that his popularity within the ranks of the people and the party is great."

Ismail, born of a peasant family in North Yemen, headed rebel commandos in the struggle for independence from Britain in the 1960s.