LONDON, Jan. 31 - Intensifying his battle with the Kremlin, the Russian oligarch Boris A. Berezovsky said today that he was just weeks away from laying out documentary evidence that Russia's security services were involved in apartment- house explosions in September 1999 that killed more than 300 people.

In an interview here, he said his investigation of the bombings, which were ascribed to separatists in Chechnya and touched off a full- scale invasion of that rebellious republic, was the reason Nikolai Patrushev, Russia's intelligence chief, accused him last week of providing financial support to Chechen "terrorists."

Mr. Berezovsky said his evidence "is no less than the evidence the United States had that Osama bin Laden was responsible for the World Trade Center attack."

He said the key to his case was the discovery in late September 1999 that Russia's security services had placed what appeared to be a large bomb in an apartment in Ryazan, 115 miles southeast of Moscow.

When residents discovered the bomb and called the police, the Federal Security Service, or F.S.B., issued a public apology and asserted that the "explosives" were actually bags of sugar tied together with wires and a detonator, a dummy used as part of a security exercise.

A number of Russian legislators called for an independent investigation of the bombings and the actions of the security service in Ryazan, but in March 2000 Parliament defeated a motion to open an inquiry. Vladimir V. Putin, a former head of the Federal Security Service, won the presidential election the same month. Mr. Patrushev succeeded him at the security service.

In the jaded politics of today's Russia, Mr. Berezovsky's claims have been treated with as much skepticism as the counterclaims of Mr. Patrushev and the security service. The fact that the charges emerged as Mr. Berezovsky was losing another battle to retain control of the independent TV6 television channel added to that skepticism.

Yet the unsolved explosions that brought terror to Russia and incited Russians against Chechens and other ethnic groups from the Caucasus stand as an enduring and troubling mystery of the Chechen conflict.

Though dozens of arrests were made in the bombings, no one has been convicted of direct complicity. Moreover, the bombings laid the groundwork for the furious military campaign against Chechnya and for the political rise of Mr. Putin, then the prime minister, whose relentless prosecution of the war garnered a surge of popular support that propelled him into the presidency.

Mr. Berezovsky said today that he had no evidence that Mr. Putin had personal knowledge of any involvement by security services in the apartment bombings, but he said Mr. Patrushev did.

"I don't have any facts today that Putin is involved personally," he said. "I have facts that the chief of the F.S.B. is involved in that, and other people from the F.S.B. are involved."

While he said the evidence implicated Mr. Patrushev, "I don't have the answer as to who gave the order - whether it was Putin, Patrushev or someone else."

The resurrection of the case highlights the tenacity of Mr. Berezovsky, the consummate Kremlin insider in the era of President Boris N. Yeltsin. From exile here, where he is fighting legal battles over his holdings and an arrest warrant issued last fall, he continues to strike at Mr. Putin in the name of liberal and democratic causes, even when many liberals shun him.

And in the end, there is the question of whether Mr. Berezovsky is simply trying to orchestrate a political crisis for Mr. Putin to win political asylum in Britain as a means to protect permanently the wealth he carved out of Russia in the early days, when the pickings were easy.

Mr. Berezovsky responded to this question by saying, "You won't have to wait long" to judge the merit of his case. He would not discuss whether he planned to seek asylum, but said he would be in danger if he returned to Russia.

"I don't want to tell you that I expect that they would kill me," he said. "I am not able to say that. But I cannot exclude anything."

Mr. Berezovsky works these days out of a suite of offices on fashionable Savile Row, where he manages a business empire that is as hard to define as it is to measure in value. But over the last decade he is believed to have controlled major stakes in Russian automobile enterprises, oil and aluminum companies, Aeroflot and ORT, the state television combine, from which he was ejected after Mr. Putin became president.

Last week, after Mr. Berezovsky lost a battle to keep TV6 on the air with a crew of journalists who had fled the independent NTV network, the security director, Mr. Patrushev, surprised him with a new assault.

Speaking in a televised interview, Mr. Patrushev said his bureau had information that Mr. Berezovsky was involved in financing Chechen rebels.

"This applies primarily to the funding of unlawful armed formations and their leaders," he said, adding that his agency planned to "duly document" the charges and relay the information "to our partners abroad, and wait for a proper reaction from them."

The next day, the security agency's spokesman, Aleksandr Zdanovich, said at a news conference that Mr. Berezovsky "is financing terrorist activity" in Chechnya.

Responding to the allegations, Mr. Berezovsky admitted that he has had extensive contacts with Chechen separatist leaders, especially from 1997 to 1999, when he was deputy national security adviser to Mr. Yeltsin and later a Kremlin adviser.

He admits giving $2 million of his own money in 1997 to a Chechen field commander, Shamil Basayev, when Mr. Basayev was serving as Chechnya's prime minister. The money was intended for restoration of a cement factory, he said, but he admitted it might have been used for other purposes.

"It was not my function to control how he spent the money," Mr. Berzovsky said, adding that Russian security officials were aware of the gift at the time, though they were not pleased about it.

Mr. Berezovsky was also involved in negotiating the release of kidnap victims in Chechnya. He said he won the freedom of 64 hostages, though he was criticized at the time for reportedly paying ransoms that fueled the kidnapping trade.

He denied paying ransom in all but one case, involving NTV journalists, but he admitted he provided substantial aid in the form of computers and other marketable goods.

Despite the controversial nature of his involvement, Mr. Berezovsky was praised by senior Russian officials, including Mr. Putin's current national security adviser, Vladimir Rushailo, for his efforts to free captives in the mid-1990's. The British government also had good things to say.

Even today, Mr. Berezovsky maintains contact with Chechen separatist leaders. He met here on Wednesday with Akhmed Zakayev, the envoy of the Chechen president, Aslan Maskhadov, whom Moscow brands a terrorist and no longer recognizes.

"I am helping him to recover his health," Mr. Berezovsky said. "He was wounded during the war and is now in the hospital. If they call that help for terrorists, then it is so."

Mr. Berezovsky said he decided to go public with his accusations of official complicity in the apartment bombings because he feared the Kremlin would try to block the effort. Though Russian newspapers have reported that Mr. Berezovsky will present his "proof" in a filmed documentary in February, in the interview he said he would not discuss the format.

"My goal is to initiate a real investigation," he said.

He then read aloud from a letter that he and members of Parliament received on Jan. 2 from the daughters of a woman killed in one of the Moscow explosions.

"Please help us to find out who killed our mother," wrote the women, Tatiana and Yelena Morozov.

"No one has replied to this letter," he said.

By PATRICK E. TYLER