British media organizations are challenging a government secrecy bid for parts of an inquest into the death of a former Russian intelligence agent poisoned in London.

Alexander Litvinenko died in November 2006 after drinking tea laced with the radioactive isotope polonium-210.

Litvinenko was a Russian agent who had turned Kremlin critic. Lawyers for his family say that at the time of his death he was working for the British intelligence services.

Britain accuses two Russians for the killing, but Moscow authorities refuse to extradite them.

The inquest is due to start in May, and the government is seeking to have some evidence heard in private because of national security concerns.

The BBC says it and other media organizations will challenge that request at a court hearing Tuesday.