Security Service spokesperson Olena Hitlianska said on Facebook, Censor.NET reports.
"SBU has revoked citizen of Ukraine V. Ruban's permit to cross the line of contact," she said.
On Feb. 24, a video was released on YouTube with independent Verkhovna Rada MP Nadiia Savchenko visiting Ukrainian prisoners in the occupied Donbas.
Earlier, militants of the so-called "Donetsk People's Republic" reported Volodymyr Ruban and Nadiia Savchenko had arrived in the occupied area of the Donetsk region "to visit Ukrainian POWs."
Today, the SBU questioned Ruban in connection with his violation of the demarcation line crossing procedure.