KYIV -- A mob of Ukrainian nationalists has seized a Brazilian man who fought for Russia-backed separatists in eastern Ukraine and had been living secretly at a Kyiv monastery since being abruptly released from prison in December.

The group frog-marched 33-year-old Rafael Lusvarghi to the doors of the Ukrainian Security Service (SBU), apparently set on returning him to custody despite a court decision.

The May 4 incident was the latest dramatic twist in the case of Lusvarghi, who had been convicted by Ukrainian authorities on terrorism charges but released in December after 14 months in prison.

An RFE/RL reporter discovered his location at the Kyiv monastery and interviewed him last month for stories that were published on May 3 in English and Ukrainian.

The men, some of whom appeared to be members of a far-right militia known as the Azov Battalion, barged into the Svyato-Pokrovskyy Holosiivskyy Monastery on May 4, live-streaming as they searched his room, taking documents and a journal. They also spat at the feet of a priest, and chanted: "Glory to the nation, death to enemies!"

They later frog-marched Lusvarghi through Kyiv’s streets, bent over at the waist, his hands tied behind his back, to the SBU's headquarters. He did not appear to have been beaten, and was also given water to drink.

WATCH: Ukrainian Nationalists Seize Brazilian Man (natural sound)

Some of the men appeared be members of an ultranationalist group known as C14, which is known for its neo-Nazi ideology.

At one point, the group forced Lusvarghi to call for Russian President Vladimir Putin to exchange him for Ukrainian prisoners being held by Russia-backed separatists.

An SBU representative later met with the crowd outside the service headquarters and promised a further investigation. Lusvarghi was then taken into SBU custody, but his whereabouts weren’t immediately clear.

The Brazilian Embassy in Kyiv had no immediate response to questions about Lusvarghi's status.

Lusvarghi left eastern Ukraine via Russia and returned to Brazil in the summer of 2016, with the battle lines in Donbas mostly frozen but skirmishes creating casualties almost daily.

Then he decided to return to Ukraine later in the year, following what he would soon discover was a false job offer from the SBU.

He was arrested upon arrival at Kyiv's Boryspil International Airport that October and put on trial. He was the first non-Russian convicted in Ukraine for crimes related to the war.

Confronted by an RFE/RL reporter at the monastery on April 30, Lusvarghi initially denied his identity. He then said he was unclear on the reasons for his sudden release from prison in December but added that his passport remained in the hands of Ukrainian authorities as they investigated his case.

The Ukrainian Justice Ministry, the Prosecutor-General's Office, and the SBU did not respond to requests at the time to clarify his status and that of the investigation.

