A Chechen refugee killed in Vienna last month was the key witness in an Austrian criminal investigation into Chechen President Ramzan Kadyrov that could have led to Kadyrov's arrest last year, prosecutors and lawyers said Wednesday.

The revelation fuels speculation that the killing of Umar Israilov, a former bodyguard of Kadyrov, was aimed at silencing a vocal critic of the Chechen leadership. Israilov was gunned down on Jan. 13, just four days after The New York Times informed the Russian government that it was planning to publish a report based on interviews with him implicating Kadyrov of murder and torture.

The case raises new questions about Kadyrov, whom human rights groups have accused of gross human rights violations for years, and threatens to create a headache for the Kremlin, which installed Kadyrov as president after his father, former Chechen President Akhmad Kadyrov, was assassinated in 2004.

Austrian prosecutors investigated Ramzan Kadyrov on human rights violations last year and sent a final report to the Justice Ministry last fall, said Gerhard Jarosch, a spokesman for prosecutors in Vienna.

Jarosch refused to reveal if charges would be made or if the case would be dropped.

"The investigation is technically closed, but we have to wait for a formal reply from the ministry," he said by telephone from Vienna.

He indicated that charges were unlikely, noting that Austrian courts "probably had no competence" in cases where "Chechens torture Chechens in Chechnya."

Jarosch also confirmed a report in Vienna's Der Falter magazine that human rights lawyers had unsuccessfully tried to get Kadyrov arrested during the Euro 2008 football championship.

Israilov last year offered information implicating Kadyrov of torture and murder to a team of lawyers in Austria and Germany, who in turn asked Vienna prosecutors to arrest Kadyrov during an expected visit to Austria for the European football championship, the Berlin-based European Center for Constitutional and Human Rights said Wednesday.

"On June 13, we filed a complaint against Ramzan Kadyrov for torture and other cruel abuse. Israilov was the key witness," the center's head, Wolfgang Kaleck, said in a statement.

The Russian national football team played against Greece on June 14 in the Austrian city of Salzburg.

Kaleck said Kadyrov had planned to travel to Salzburg for the match and the lawyers therefore had decided to seek an arrest warrant. But when they contacted Vienna prosecutors late in the day, they were told that the case was not urgent enough.

Jarosch said there were doubts about whether Austrian authorities were within their jurisdiction and whether Kadyrov was protected by immunity.

A senior Austrian prosecutor, Werner Peischl, was quoted by Der Falter as saying that "we cannot arrest a president just because a lawyer wants us to."

Around the same time as the request for the arrest, Austrian police arrested a Chechen man who claimed that he had been sent by Kadyrov to kill Israilov, Der Falter reported Wednesday, citing police records.

Jarosch said the case of the Chechen man was not pursued because Austrian prosecutors believed and still believe that they lack jurisdiction.

Both Austrian prosecutors and Chechen officials said Kadyrov never traveled to Austria last year.

"I do not know whether such a visit was ever planned, but I do know that the president did not go," Timur Aliev, an adviser to Kadyrov, said by telephone from Grozny.

Jarosch said there had been speculation, "but to my knowledge he never came."

Kadyrov has denied having anything to do with Israilov's death. He told Rossiiskaya Gazeta in an interview published Tuesday that the murders of Chechens in Europe were committed by the "enemies of Chechnya."

Russian regional leaders have no immunity from prosecution.

Rights activists accused Austrian authorities of turning a blind eye to crimes against humanity and having fatally played down the danger for Israilov. "Only days before he was murdered, police refused to give extra protection for Israilov," Kaleck said in the statement.

Kaleck was unavailable for comment Wednesday, but Kamil Majchrzak, a fellow lawyer at his center, said Austria had an obligation to act decisively in such cases because the alleged crimes were not being prosecuted in Chechnya.

"Every country must act if there is a relation. In this case, if Kadyrov enters the territory of Austria, there is such relation" Majchrzak said by telephone from Berlin.

He said Israilov's death was devastating because it was extremely difficult to find witnesses to abuses in Chechnya.

"Not just did he have firsthand evidence, but his case had also been acknowledged by authorities in Austria who granted him political asylum," Majchrzak said.

An estimated 20,000 Chechens live in Austria, making it home to the largest Chechen refugee population in Europe.

Prosecutors have arrested seven suspects in Israilov's death, all ethnic Chechens, and five remain in prison, Jarosch said. He said it was not clear whether the killer was among them.

nChechen separatist leader Akhmed Zakayev has turned down an offer by Kadyrov to return to his homeland from exile in London.

Zakayev said he would only go back if a political solution for the coexistence of Russia and Chechnya had been found, the BBC's Russian service reported on its web site.

"To negotiate about some posts in today's Chechnya would be very stupid, to say the least," Zakayev was quoted as saying in an interview.

Kadyrov said in the Rossiiskaya Gazeta interview that Zakayev had told him that he wanted to return.