Russian prosecutors lodged charges of conspiracy to commit murder Monday against Leonid Nevzlin, the second-largest shareholder in the parent firm of Yukos Oil Co., raising the stakes in the government's campaign against the oil firm and its owners.

A Moscow court issued an arrest warrant for Nevzlin, accusing him of ordering a series of contract killings of people perceived to be obstacles to the business.

Nevzlin, who fled last fall to Israel to evade another warrant on financial charges, denied the latest allegations through his attorney.

Nevzlin is a longtime business associate of Mikhail Khodorkovsky, the oil tycoon who is the largest shareholder in Yukos's parent company, Group Menatep. Khodorkovsky is currently on trial in Moscow on charges of fraud and tax evasion.

The charges against Nevzlin are "obviously political," Dmitri Kharitonov, his attorney, said in a telephone interview. "He did not participate in any of these murders. The charges that have been brought are absolutely absurd. They cannot be proved, and they're groundless."

Khodorkovsky issued a statement through his attorney calling the charges "monstrous."

The charges stem from allegations that have never been formally pressed against Nevzlin, and the timing of the warrant -- just as the government is preparing to seize and sell Yukos's primary oil production unit -- suggested that the state did not want to find an amicable settlement deal, as many investors had hoped.

The news further alarmed investors, who were already shaken by last week's announcement that the state, to satisfy a back-tax claim, would confiscate the subsidiary that pumps 60 percent of Yukos's oil. Stock in Yukos fell 21.5 percent, to $4.20 a share, on the benchmark RTS index and almost as much on the ruble-denominated MICEX market, where officials halted trading because of the precipitous decline.

According to the most recent public statement in 2002, Nevzlin owned 8 percent of Group Menatep; Forbes magazine this year estimated his personal fortune at $2 billion.

Russian prosecutors painted a picture Monday of a business boss knocking off anyone who got in his way. In a statement, they alleged that Nevzlin conspired with Yukos's security chief, Alexei Pichugin, who has been under arrest for more than a year without being put on trial, to murder two people in separate hits in 1998 and a third person in 1999.

None of the victims actually died, either escaping with a beating because bystanders happened on the scene or surviving explosions set off near them.

But prosecutors alleged that Nevzlin subsequently ordered the murder of the man Pichugin used for the hits. Both Sergei Gorin and his wife were killed and their corpses removed to an unidentified place, the prosecutors said.

They alleged that Nevzlin and Pichugin decided to have their hit man murdered "because they realized the danger coming from Gorin, who had documents and information on their involvement in those events."