Oleksandr Ponomaryov, a lawmaker elected for a now-banned party accused of ties to Russia, was placed in detention without bail by Kyiv's Pechersk district court, the prosecutor's office said.

Ponomaryov has denied collaborating with Russia in the past.

A lawyer for Ponomaryov could not be immediately reached for comment on Tuesday.

The Security Service of Ukraine said in a statement that Ponomaryov had "willingly collaborated" with Russia when he was in the occupied part of the Zaporizhzhia region.

The spy agency accused the lawmaker of re-registering his businesses in the area under Russian laws, transferring money into local branches of Russian banks, supplying the Russian military with "fuel-oil materials" for their vehicles and of providing equipment used to make fortifications.

Schemes, a Ukrainian investigative media outlet affiliated with RFE/RL, published an article on Monday that said Ponomaryov had spent six months in Berdyansk, a port city in Zaporizhzhia region that was seized by Russian forces in the early days of the February 2022 invasion.

Ponomaryov said in an interview published as part of the article that he had been detained by Russian forces on March 20, 2022, imprisoned and tortured. He said he declined offers to collaborate with the Russians, both for his businesses and himself, after which he said all his businesses were seized and were now controlled by Russia.