MOSCOW (AP) _ About 4,200 inmates have been released from Russia's notoriously overcrowded pretrial detention centers over the past month, Prime Minister Vladimir Putin said Tuesday.

Putin made the announcement during a conference call with prison officials. He said the move would improve conditions in the jails, where tuberculosis and other illnesses are common and suspects often wait more than two years in overcrowded cells for their trials to begin.

It was unclear if the inmates were released on bail awaiting trial or for lack of evidence in their cases. Putin said the release was ``in conformity with the law,'' according to the ITAR-Tass news agency. He encouraged releasing more suspects.

Putin said the move will ``save the health or, perhaps, even the lives of those people'' released, according to ITAR-Tass.

About 1.1 million people are incarcerated in Russian prisons and pretrial detention centers.