MOSCOW — Aleksandr Y. Lebedev, a prominent banker and newspaper magnate who has supported the political opposition, announced on Friday that police and regulatory checks had become so intense that he would sell all of his Russia-based assets.

“The special services steamrolled my businesses into the pavement,” Mr. Lebedev told the Interfax news agency. “I give up.”

If he indeed divests himself of Russian assets — he said it might be difficult to find buyers, given the controversy — Mr. Lebedev will be joining a dozen or so other post-Soviet billionaires who lost fortunes or at least moved them out of Russia after public disputes with President Vladimir V. Putin. Mr. Lebedev had for years gotten away with tweaking the president in public, with humor and sponsorship of a dissident newspaper, perhaps because he is, like Mr. Putin, a veteran of the Soviet K.G.B. with deep roots of his own in the Moscow political elite.

In one of several interviews with Russian and foreign media outlets in which he made the announcement on Friday, Mr. Lebedev, 52, said he would reduce his exposure to Russian investments to “zero.” Forbes magazine reported his net worth at $1.1 billion, though not all of it was invested in Russia.