Ukrainian President Volodymyr Zelensky asserted Friday that a group of Russians and Ukrainians planned to attempt a coup in Ukraine next month and that the plotters tried to enlist the help of the country’s richest man, Rinat Akhmetov.

Zelensky, speaking at a “press marathon” for local and international media, said that audio recordings, obtained by Ukraine’s security services, caught plotters discussing their plans and mentioning Akhmetov’s name.

Akhmetov was not involved in the purported coup plot, however, Zelensky said.

The president offered no other details, however, leaving many questions about his motives for making the allegations public and what possible actions authorities have taken.

Akhmetov, a mining and steel tycoon, also owns media holdings, which in recent weeks have increased their criticism of Zelensky and his administration.

A statement attributed to Akhmetov called Zelensky’s claims “an absolute lie.” Kremlin spokesman Dmitry Peskov denied any Russian role in an alleged plot.

“Russia never engages in such things. There have never been such plans,” Peskov said.

Zelensky’s comments also come against a backdrop of rising tensions between Kyiv and Moscow.

Western and Ukrainian officials say that they have observed a buildup of Russian forces on the country’s border with Ukraine.

The reasons for the buildup are unclear, but U.S. and other officials say that it could be preparation for an invasion or an escalation in the seven-year-old conflict in eastern Ukraine with anti-Kyiv insurgents, backed by Moscow, according to Western officials and independent researchers.

Speaking in Nantucket, Mass., President Biden told reporters that he would “in all probability” have talks with Zelensky and Russian President Vladimir Putin over the deepening tensions.