Farida Islamova is claiming the money as compensation, Nevzlin's lawyer said.
Investigators allege that between 1998 and 2002, members of an organized criminal group headed by Nevzlin murdered, among others, Nefteyugansk mayor Vladimir Petukhov and businesswoman Valentina Korneyeva.
Petukhov, a Yukos critic, was shot along with his driver on the way to his office on June 26, 1998. A Yukos employee, Alexei Pichugin, was subsequently charged with the murder. Pichugin is serving life in prison for murders and attempted murders. He maintains his innocence.
Before his murder, the mayor of Nefteyugansk had been on a hunger strike demanding that the chairmen of municipal and district tax offices be dismissed from their positions and a criminal case against Yukos be filed on counts of tax evasion. His widow has claimed that the then-head of Yukos, Mikhail Khodorkovsky, was also implicated in the murder, and has called for an investigation into his role in events.
"The company had evaded local tax payments and hid its earnings from the public. Khodorkovsky managed to solve the problems through bribing important officials. The local budget and survival of the town completely depended on the tax revenues from Yukos. The town was left with no revenues and no means to survive," Islamova said earlier.
Petukhov's murder took place on Khodorkovsky's birthday, and soon after the shooting, local residents took to the streets, attempting to storm the local office of Yukos.
Nevzlin, who fled to Israel in 2003, has denied all the charges. Israel has refused to extradite him, demanding more evidence. He is being tried in absentia.
Once Russia's largest oil producer, Yukos collapsed after being charged with tax evasion, which led to the company being broken up and sold off to meet debts. The bulk of the company's assets were bought up by state-run oil company Rosneft.
Khodorkovsky and his business partner Platon Lebedev were found guilty of tax evasion and large-scale fraud by a Moscow court in May 2005 and sentenced to nine years in prison. The Moscow City Court later reduced their terms to eight years.
The two men are serving their sentences in Eastern Siberia. Both men have maintained they are innocent, with Khodorkovsky claiming the sentence was retaliation for his support of Russia's tiny opposition movement.
The jailing of Khodorkovsky and other Yukos executives has been widely criticized in the West and seen as part of the Kremlin's drive to regain lucrative energy assets.
Russian President Dmitry Medvedev recently hinted that Khodorkovsky could eventually be pardoned.
Petukhov's widow has claimed that her husband's murder has been overlooked in Europe in the clamor to criticize the Kremlin over Khodorkovsky's imprisonment.
"It is hard to find a PACE deputy or a notable representative of any authoritative European organization who has never spoken about the so-called Yukos case," she said, saying that her husband and other people alleged to have been murdered on the orders of Nevzlin were the forgotten "victims" of the Yukos saga.