(AP) – Russia’s non-governmental organizations on Thursday demanded President Vladimir Putin prove they received nearly $1 billion from foreign sponsors, a claim he has used to justify sweeping raids on hundreds of groups.

The crackdown has drawn strong criticism from the West as a political witch hunt, but Putin insists it is necessary to check compliance with a new law that requires NGOs that receive foreign funding to register as “foreign agents.”

Leaders of top Russia’s NGOs, including human rights group Memorial, election-monitoring group Golos and more than 50 others, dismissed the $1 billion figure as inflated and called on him to document it.

“The figures that you mentioned are at least dozens of times higher than what we know about the amount of foreign support for NGOs in Russia, and we would like to know what organizations receive such big money,” they said in an open letter to Putin.

They urged him to order authorities to publish a list of the NGOs that received the foreign funds.

Putin highlighted the figure in a recent TV interview and his trip to Germany this week, insisting that the public has the right to know who funded them and for what purpose. He offered no detail on where the figure came from, but other officials said it came from law enforcement agencies.

Putin, who won a third presidential term in March 2012, has used the term “foreign agents” to erode NGOs credibility in Russia, where suspicion of the West runs high.

He has accused the U.S. of fomenting protests against his rule in order to weaken Russia and described NGOs as an instrument of Western pressure.

Russia’s top NGOs have pledged to boycott the new law, but authorities said that those who disobey would face sanctions.

The Justice Ministry said this week that it is filing a legal case against Golos, the country’s only independent elections monitoring group for allegedly failing to register as a foreign agent. Golos has dismissed the claim, saying that it has not received foreign funding since the law took effect.

Under the law, failure to register carries a potential fine of up to 300,000 rubles (about $9,500) for the organization’s director and 500,000 rubles ($16,000) for the organization.

The U.S. State Department has condemned the searches of NGOs as a “witch hunt” and German Chancellor Angela Merkel voiced strong concern about the crackdown during Putin’s visit.