The killing of top Chechen rebel Aslan Maskhadov (search) leaves the insurgency largely in the hands of Shamil Basayev (search), the most brutal of the warlords — a development that could undermine any chance of peace even as the Kremlin celebrates a success in the long conflict.

On Wednesday, there was uncertainty over what the death might mean, with Russia facing the fundamental question of how much an insurgency depends on its leaders — a dilemma faced by Israel in the targeted killings of key Palestinian militants and the United States in the hunt for the top men in Al Qaeda (search).

Russia hopes the Chechen insurgency might be hobbled, with a series of militant leaders systematically eliminated over the years. In recent months the Russians also appear to have reaped some gains from a tough policy that apparently includes detaining rebels' relatives.

And the Chechens might suffer diplomatically too, because Maskhadov was respected by some European mediators as a possible negotiator — a mantle not likely to pass to Basayev. The death of the more moderate Chechen leader could leave the Europeans with no major figure they can push the Russians to negotiate with.

In Russia, some legislators hailed Maskhadov's killing as a sign that Russia, which has suffered repeated terrorist attacks, might be on the right track at last.

"When terrorists feel they are literally being trailed, fighting groups are systematically being detained, when in fact a top leader is eliminated, this creates an atmosphere in which there's no place for terrorist attacks," said Vladimir Vasilyev, head of the security committee of the lower house of parliament.

But there appeared to be the prospect of a stepped-up Chechen effort to avenge the killing and to prove the cause lives on.

"Certainly I think military activity will be activated," Maskhadov's London-based envoy Akhmed Zakayev told The Associated Press, echoing the threats of other militants. "It will be planned operations that will be carried out by our armed forces as long as the Russian occupiers continue violence in Chechnya."

Even some supporters of the Kremlin campaign seemed to doubt it would force an end to attacks — especially since Maskhadov was believed to directly control comparatively few of Chechnya's estimated 1,500 rebels.

"I don't think Maskhadov's death is such an irreplaceable loss for the rebels," said Aslambek Aslakhanov, a Chechen who serves as Russian President Vladimir Putin's (search) special adviser on the North Caucasus region.

But diplomatically, Maskhadov's loss may have real impact.

He was seen as a relative moderate in comparison with the Islamic fundamentalist Basayev and had repeatedly called for negotiations to end the fighting. His suggestion that compromise was possible — and the fact that he was Chechnya's elected president for a brief period of de facto independence and relative calm — lent him credibility and support among Chechens tired of the conflict.

"For me, the death of Maskhadov is a great pain. He was aiming for peace and wanted to achieve it, but the Kremlin didn't want this," said a resident of the Chechen capital Grozny, who gave his name only as Shudin.

Maskhadov was blamed by the Russians for terrorist acts, but he usually denied the accusations.

A string of Chechen leaders were killed earlier, including President Dzhokhar Dudayev, who died in the war after declaring independence in 1991; rebel leader Zelimkhan Yandarbiyev, assassinated in Qatar in February 2003; and the Moscow-backed president, Akhmad Kadyrov, who was blown up in Grozny last May.

Basayev, meanwhile, has taken part in and claimed responsibility for some of the deadliest recent attacks, including the school seizure in Beslan (search) that killed some 330 people last year and the 2002 seizure of hundreds of hostages at a Moscow theater.

During the school seizure, leaders of the raid reportedly killed several accomplices who objected to taking children as hostages, revealing Basayev to be too radical even for some of his accomplices. Such extremism could undermine his ability to unite the smaller groups which have been successfully striking Russian forces.

Russia can now step up the hunt for Basayev, its most-wanted fugitive, who has more than a decade of experience in evading Russian dragnets.

In any case, with Maskhadov's "violent death ... a new period has begun in the modern history of the Russian-Chechen military confrontation, which not only allows for no negotiations, but also for no end to the war," rebel ideologue Movladi Udugov wrote on a rebel Web site, Kavkaz Center.

Zakayev suggested the new phase could bring more terrorist attacks, saying: "It's my personal fear that the radical part of the Chechen resistance, after what happened yesterday, will feel its hands untied and freed from any moral responsibility."

Polish Foreign Minister Adam Rotfeld called the killing "a political mistake because ... Maskhadov was the only partner with whom an agreement could be sought." He added: "I do not exclude that those who carried out the killing wanted to cross out the possibility of an agreement."

The Council of Europe said it regretted the killing and urged that "the effort to find a political solution to the situation in Chechnya must continue."

Undermining the prospect is the increasingly jittery atmosphere in Chechnya, where violence attributed to the pro-Kremlin local security forces is expected to spread.

Those forces are alleged to have abused and abducted civilians, including some of Maskhadov's relatives, reportedly in an attempt to induce him to surrender.

Recent months have seen an upsurge in clashes between Islamic militants and federal Russian forces in practically every republic in the Caucasus Mountains region — fighting not directly linked to Chechnya, but perhaps inspired by the conflict there.