The death of Hermitage Capital hedge fund lawyer Sergei Magnitsky in a pretrial detention center was partly the fault of Russia's Federal Penitentiary Service, a top prison official admitted Thursday.

Magnitsky, who was awaiting trial on tax evasion charges, died in a Moscow pretrial detention center earlier this month. The Russian Prosecutor General's office said that he died of a heart attack. But Hermitage Capital head Bill Browder, who is also facing tax evasion charges in Russia, told the BBC earlier this week that Magnitsky was "killed" after refusing to sign a confession.

"He was their hostage and they killed their hostage by denying him medical attention," he said.

A probe into the lawyer's death was ordered by Russian President Dmitry Medvedev.

"We are not playing down our guilt in any way," Federal Penitentiary Service deputy head Alexander Smirnov said. "We will not deny violations on our part, but I would not like to draw any conclusions yet."

Investigators said Wednesday that Magnitsky had conspired with Browder, who has reportedly been banned from entering Russia, to establish dummy firms to illegally buy and sell Russian energy giant Gazprom's stock.

MOSCOW, November 26 (RIA Novosti)