A lawyer has challenged the arrest of Ukrainian citizen Roman Suschenko, who is under arrest in Russia on espionage charges, the press service of Moscow's Lefortovsky District Court told Interfax.

"We have received an appeal from a lawyer against the court resolution on the preventive measure against Suschenko in the form of custody. The lawyer requests [the court] to cancel its resolution and select a softer preventive measure against his client," Yekaterina Krasnova, spokesperson for the court, said.

Russia's Federal Security Service (FSB) reported on Monday that "Ukrainian military intelligence career officer Col. Suschenko had been detained in Moscow when gathering intelligence."

The FSB opened a criminal case on espionage charges. An investigation is underway. The Russian Foreign Ministry, in turn, said that the detainee was in Russia without a journalist accreditation.

The Moscow Lefortovsky Court ordered a two-month arrest of Suschenko.

Kyiv said that the detention was an act of provocation and the accusations of spying were groundless.