A Ukrainian lawmaker said Sunday he was detained by Russian police ahead of a Moscow march to honour opposition leader Boris Nemtsov, who was gunned down near the Kremlin.
The parliamentarian, Alexei Goncharenko, was later released from police custody, but must appear before a tribunal on Monday and could still face detention, his lawyer said.
"Police have detained me," Goncharenko wrote on Facebook. "I did not shout anything, did not carry any banners or flags -- they simply detained me over the T-shirt."
According to a picture posted on Facebook, Goncharenko's T-shirt carried a printed picture of Nemtsov and said in Ukrainian: "Heroes never die", similar to a popular slogan used during last year's pro-Western uprising in Ukraine.
The lawmaker said he travelled to Russia to take part in the Nemtsov memorial rally Sunday that saw tens of thousands of people march through central Moscow.
A Russian committee of enquiry said in a statement that Goncharenko had been arrested for refusing to comply with police instructions and said questioning him was justified because of "crimes committed against a Russian citizen during the tragic events in Odessa."
Pro-Moscow supporters accuse Goncharenko, who hails from the southern Ukrainian city of Odessa, of taking part in rallies that led to the deaths of dozens of pro-Russian activists.
Some 50 people were killed in Odessa last May, with most perishing in a blaze during clashes between pro-Russian activists and supporters of Kiev.
Goncharenko's lawyer Nikolai Polozov said on Twitter later that his client had left the police station later Sunday.
He was then put in a car with diplomatic plates with Ukraine's consul to Russia, according to a Ria Novosti agency journalist.
Another Ukrainian national, Nadia Savchenko, has been held in a Moscow jail for almost nine months after being charged with involvement in the death of two Russian reporters in a mortar attack in east Ukraine.
The 33-year-old helicopter navigator denies the charges. She has been on hunger strike for nearly 80 days in protest at her detention and rights activists said late last week she could die within days.