Russian President Vladimir Putin broke his silence Monday about the brazen daylight murder of investigative reporter Anna Politkovskaya, pledging the authorities would do everything to find the killers of the fierce Kremlin critic.

In a phone conversation with U.S. President George W. Bush, Putin pledged that "all necessary efforts will be made for an objective investigation into the tragic death" of the journalist, the Kremlin said.

Putin's remarks were his first statement on the slaying, since Politkovskaya, a 48-year-old award-winning reporter who uncovered abuses against civilians in Chechnya, was gunned down in her apartment building Saturday in an apparent contract killing.

Her newspaper has offered a million-dollar reward for information that would help solve the crime, which provoked worldwide condemnation and shone the spotlight on Russia as one of the most dangerous countries for journalists.

Her colleagues said she had been working on a story about torture and abductions in the war-ravaged southern province — abuses she blamed on Moscow-backed Chechen Prime Minister Ramzan Kadyrov. "I dream of seeing him tried," she said in an interview several days before her death.

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The semiweekly newspaper Novaya Gazeta, where Politkovskaya had worked, on Monday published a special edition, listing Politkovskaya's major publications and inquiring into the cause of her killing.

The paper also said in a statement that the killing was either revenge by Kadyrov or an attempt to discredit him.

Kadyrov expressed condolences over Politkovskaya's death, and denied any "Chechen trace" in the killing.

"It is hearsay and rumors, which don't show either politicians or the media in a good light," Kadyrov was quoted as saying by the Vremya Novostei daily.

Prosecutor-General Yury Chaika has taken personal charge of the investigation, but Politkovskaya's colleagues have expressed doubts the murder will ever be solved.

Russia is the third most deadly country for journalists, after Iraq and Algeria, according to the New York-based Committee to Protect Journalists, which says Politkovskaya was at least the 43rd journalist killed for her work in Russia since 1993.

Novaya Gazeta announced a 25 million ruble (US$929,700, euro737,800) reward for information on the slaying and pledged to conduct an independent probe.

Investigators had originally said the attacker was believed to have acted alone, but Kommersant reported Monday he possibly had an accomplice, a woman in her thirties, who helped him follow the victim from the grocery store.

Coroners possessed a composite sketch of the killer who was wearing a cap based on footage recorded by a security camera at Politkovskaya's apartment building and police were hunting for the suspects Monday.

U.S. President George W. Bush joined the international chorus of condemnation.

"Like many Russians, Americans were shocked and saddened by the brutal murder of Anna Politkovskaya, a fearless investigative journalist, highly respected in both Russia and the United States," Bush said Sunday.

"We urge the Russian Government to conduct a vigorous and thorough investigation to bring to justice those responsible for her murder."

Among others, the European Union and the Council of Europe rights watchdog have also expressed their condolences and called for a far-reaching probe.

In Germany, where Putin heads Tuesday for a summit with Chancellor Angela Merkel, Foreign Ministry spokesman Martin Jaeger said the killers and those behind the slaying must be found and punished. "Beyond that ... it is the task of a government to ensure that a climate of fear in which press freedom cannot develop does not arise in a country," he said.

Politkovskaya's death was the most high-profile slaying of a journalist in Russia since the July 2004 assassination of Paul Klebnikov, the U.S.-born editor of the Russian edition of Forbes magazine.

Politkovskaya, whom Vremya Novostei described as a member of a disappearing breed of courageous investigative reporters, will be buried in Moscow on Tuesday.