A Russian human rights lawyer is alleging she and her family have been poisoned by a suspicious substance found in her car.

Karinna Moskalenko says the alleged poisoning has made her too ill to attend Wednesday's opening day of a trial in Moscow of three men accused of slaying journalist Anna Politkovskaya.

Human rights and media groups described the incident as an apparent attempt to intimidate Moskalenko, who has represented Kremlin foes, including chess champion Garry Kasparov.

Moskalenko told Ekho Moskvy radio on Tuesday that she and her children have had headaches, dizziness and nausea over the last few days.

She also alleges her husband found a significant amount of a mercury-like substance in their car Monday in Strasbourg, France.

She said she had been hospitalized for testing, and alleges doctors had given her and other family members a preliminary diagnosis of poisoning.

Moskalenko could not immediately be reached for comment Wednesday. She told Ekho Moskvy it may have been an attempt to frighten her, and did not rule out a connection to the Politkovskaya murder trial.

1st trial in journalist's killing

Politkovskaya, whose reports on human rights abuses in Russia and especially Chechnya embarrassed the Kremlin and its allies, was shot to death in her Moscow apartment building in October 2006.

This is the first trial held in connection with the journalist's killing. It has already been marred by the absence of the suspected triggerman, who prosecutors say has fled to western Europe, and the lack of an answer to the crucial question of who was behind the killing.

Several Russians who have criticized or angered the Kremlin — including Politkovskaya herself — have been victims of alleged poisoning attacks in recent years.

Politkovskaya fell seriously ill with food poisoning after drinking tea on a flight from Moscow to southern Russia in 2004, which prevented her from covering the hostage crisis in Beslan in which more than 330 people were killed. Kremlin critic Alexander Litvinenko died of radiation poisoning in Britain in 2006, weeks after Politkovskaya was gunned down.

Moskalenko is a lawyer for Politkovskaya's family and for imprisoned former oil tycoon Mikhail Khodorkovsky. She also represented Kasparov after he was detained last year during an anti-Kremlin protest.

Moskalenko spends much of her time helping Russians press claims against the government at the European Court of Human Rights in Strasbourg, which puts her at the forefront of challenges to Russia's international image. Last year, she weathered an attempt to have her disbarred.

Calls for trial to be open to the public

The suspects being tried on murder charges are Sergei Khadzhikurbanov — a former police officer with Moscow's anti-organized crime unit — and Makhmudov's brothers Ibragim and Dzhabrail.

They are being tried together with Pavel Ryaguzov, a former Federal Security Service officer accused of criminal links with Khadzhikurbanov.

The chief investigator in the case has said prosecutors believe Khadzhikurbanov organized details of the killing, and that one Makhmudov brother followed her and fed information on her movements to the other, who was near the site of the killing and passed the details along to the shooter.

The trial is being held in a military court.

Relatives and colleagues of Politkovskaya are calling for the trial to be open to the public, but RIA-Novosti news agency quoted defence lawyer Murad Musayev as saying it appeared likely it would be closed.

That decision will be made at the next session, Musayev said.