Russian prosecutors are searching the offices of Memorial, one of the country's oldest and most respected rights groups, as part of a new campaign targeting hundreds of nongovernmental organizations across the country.

In a letter sent Thursday to Russia's prosecutor general, the Kremlin's presidential human rights council says it has been flooded in recent days with complaints from NGOs, and asks for an explanation.

Pavel Chikov, a member of the council, told the Associated Press that up to 2,000 organizations have been searched. He said the scale of the campaign is unprecedented.

On Thursday, prosecutors turned up without notice in the Moscow offices of Memorial, an organization that documents right abuses.

President Vladimir Putin has long been suspicious of NGOS, especially those that receive foreign funding.