Gennady Kernes, the pro-Russian mayor of Kharkiv, is seen in Kharkiv in this August 5, 2010 file photo. Kernes was in a serious condition on April 28, 2014 after being shot in the back while riding his bicycle, the latest violence in the country's east. [Photo/Agencies]

Ukraine crisis

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KIEV - The mayor of Ukraine's eastern city of Kharkiv was in critical condition Monday after being shot in the back, officials said.

Gennady Kernes, 54, was shot on the outskirts of Kharkiv, Yuri Sydorenko, spokesman for the city hall, was quoted by the Interfax news agency as saying.

The mayor was undergoing surgery and "doctors are fighting to save his life", Sydorenko said, without commenting on who could be behind the attack.

Valery Boyko, head of the county's Institute of Surgery, said Kernes' condition was serious.

"Several of his integral organs have been injured. He is suffering traumatic shock and bleeding," Boyko said.

Meanwhile, Iryna Kushchenko, spokeswoman for the local government, said Kernes was riding his bicycle along a route he takes almost every day when he was shot, probably by someone hidden in nearby woods.

His bodyguards, who were following him in a car when the attack occurred, were not close enough to intervene, she said.

Kernes was an ally of ousted President Viktor Yanukovych, but after the president's ouster, he began to cooperate with the new government in Kiev.

The mayor officially supports the territorial integrity of Ukraine and holds a position of mediator between Ukrainian authorities and pro-Russia protesters in eastern Ukraine.

Acting President Alexandr Turchynov has ordered an immediate investigation into the incident.

Also on Monday, three people were injured when a group of unidentified gunmen opened fire at a passenger bus in the northern Kiev region, the Interior Ministry said in a statement.

The attackers escaped to an unknown destination by three cars, the statement said, adding that police officers were hunting them in a nearby area.

Ukraine has been plunged into a chaotic violence since November 2013 following a government backtrack on European integration which angered many in the west of the country.

It was hit by a fresh wave of unrest after Crimea left Ukraine to join Russia last month.

Pro-Moscow demonstrators have staged protests in eastern Ukraine since early April, demanding a referendum on autonomy and closer ties with Russia.