Ukrainian security forces turned away a Russian human rights activist at Boryspil Airport in Kiev over the weekend, prompting an outcry from supporters.

The Ukrainian human rights initiative Evromaydan SOS said in Facebook posting Sunday Andrei Yurova, a member of the Russian Presidential Council on Human Rights and director of development of the Moscow Helsinki Group, was refused entry into the country by the Security Service of Ukraine, SBU, after arriving in Kiev on a flight from Moscow.

The group said Yurova arrived at Boryspil where he was informed by security officials he was "persona non grata" in Ukraine for unexplained reasons and put on plane back to Moscow.

He was traveling to Ukraine to visit the eastern regions of the country at the invitation of the Evromaydan SOS to monitor human rights, the group said, noting that Yurova in 2010 was also refused entry into Belarus while seeking to help people detained after the mass protests following the presidential election there.

The situation brought an angry response from the Russian human rights council, whose leader promised to take the matter up with the Russian Foreign Ministry, Interfax reported.

Yurova told the news service after returning to Moscow's Sheremetyevo Airport Sunday he was given no reason for his expulsion, explaining he had planned to take part in an international conference and meet with the Ukrainian human rights ombudsman.

"When I came to Ukraine, I was detained at passport control," he said. "I was told that I was persona non grata, and I was denied entry. They gave me an official paper, which stated that the decision was made by an 'authorized state body of Ukraine.' I was told verbally that the decision was made the SBU. Apparently, on some SBU lists I am seen as a particularly dangerous man."

What happened, Yurova added, "is totally unacceptable. I have never engaged in politics. I'm engaged in something that has no boundaries -- human rights issues. It is a violation of many international obligations."

Yurova is described by British non-governmental organization Rights in Russia as a human rights defender, philosopher and trainer, director of strategic programs of the Moscow Helsinki Group, honorary president of the International Youth Human Rights Movement and an expert for the Council of Europe.

As a member of Russian President Vladimir Putin's advisory human rights council, Yurova's refusal of entry into Ukraine brought a quick response from the group's chief, Mikhail Fedotov. He announced Sunday the council would send a formal request to the Russian Foreign Ministry in connection with the incident.

"Such an attitude toward Russian human rights activists by the authorities of any country we find to be unacceptable, but from a fraternal country such as Ukraine, it is just shocking," he told Interfax. "On Monday, we will write a formal letter to the foreign ministry, so that through diplomatic channels the situation can be resolved immediately."

Fedotov said he had alerted Russian human rights ombudsman Vladimir Lukin and had spoken to diplomats about the incident.

"I believe that the Ukrainian authorities should be interested in the fact that human rights defenders can provide objective information about world events in Kiev and other regions of the country," he said.

The incident came as the SBU announced it was putting its anti-terrorism forces on alert in the wake of "a sharp rise" in unspecified threats against nuclear power plants, airports and gas and oil pipelines.