Russian Deputy Foreign Minister Sergei Ryabkov said on Thursday it was too early to talk of a possible prisoner swap involving detained U.S. reporter Evan Gershkovich who has been held on suspicion of spying, the state RIA news agency reported.

The Interfax news agency cited Ryabkov as saying that such exchanges had previously taken place for those already convicted, and that it was necessary to wait to see how the story with Gershkovich developed.

Russia's FSB security service said on Thursday it had detained Gershkovich, a reporter for U.S. newspaper The Wall Street Journal, on suspicion of spying for Washington, the most serious public move against a foreign journalist since Russia invaded Ukraine.

The Wall Street Journal has said it vehemently denies the allegations against him.