* Dagestani fighter found guilty of manslaughter of ethnic Russian
* Police on alert in central Moscow
* Nationalist sentiment rising in Russia
By Maria Tsvetkova
MOSCOW, Nov 27 (Reuters) - An ethnic Dagestani martial arts fighter was spared jail on Tuesday by a Moscow court that found him guilty of the manslaughter of an ethnic Russian in a case that could fuel protests on the anniversary of nationalist riots.
Riot police were on alert after the ruling and restricted access to Manezh square, scene of Moscow's worst ethnic violence in post-Soviet history on Dec. 11, 2010.
Police detained several nationalists outside the court where some were shouting chants urging people to gather in Manezh square again, RBC news agency said.
The violence in 2010 was triggered by a killing of soccer fan Yegor Sviridov by a group of migrants from the Northern Caucasus, which includes Dagestan, and nationalists are planning rallies on the anniversary.
President Vladimir Putin is facing a difficult balancing act between rising Russian nationalism and the interests of national republics with large ethnic diasporas in big cities.
Some analysts regard radical nationalism as the single biggest threat faced by the country, which is home to more than 160 distinct national and ethnic groups.
Professional fighter Rasul Mirzayev, who fought under the name "Black Tiger", killed ethnic Russian Ivan Agafonov in August 2011 in a brawl outside a Moscow night club.
The court ruled that Mirzayev had used his skills when hitting Agafonov, who fell on the pavement injuring his head, lost consciousness and later died in hospital.
Under the conditions of his release, Mirzayev will have to regularly report to police and stay in his home region.
"I was really very surprised, I did not think I would be released, I was sure that I would stay in jail," Mirzayev told Lifenews Internet portal from his courtroom cell. "First thing I want is to go see my mother and daughter."
Agafonov's relatives, who shouted "shame, shame" when the fighter was ushered out of court after the judge read the verdict, said they would appeal against the decision.
Riot police restricted access to the square after some nationalist politicians warned of the possibility of new riots. Interfax news agency said similar calls were made by nationalist on social networks.
"People's discontent is rising. One should not forget that Dec. 11 is the Manezh square anniversary," said nationalist politician Alexander Belov.
Putin remained silent on the court ruling on Tuesday. After the 2010 riots Putin, then prime minister, sought to pacify soccer fans by laying flowers at the grave of the murdered fan.
Aslan Cherkesov, the man who killed Sviridov, was sentenced to 20 years in prison. (Writing by Gleb Bryanski; Editing by Alison Williams)