RUSSIA’S SECURITY services held two men on Saturday on suspicion of murdering Boris Nemtsov, the Kremlin critic who was shot in the back near Red Square, prompting a worldwide outcry.

In televised comments, Alexander Bortnikov, the director of the Federal Security Service, said Anzor Gubashev and Zaur Dadayev were taken into custody on Saturday. Mr Bortnikov confirmed the suspects were “residents of the Caucasus”, other state media reported.

Vladimir Putin, Russia’s president, who took personal control of the investigation, had been informed, he said.

The Investigative Committee, the state body that is formally leading the effort to solve the crime, confirmed the two men were suspected of involvement in the “organisation and execution” of the murder, but said the investigation was continuing.

Mr Nemtsov, 55, a former deputy prime minister and a strident opponent of Mr Putin, was shot four times in the back on February 27 as he walked home across a bridge near the Kremlin with his girlfriend, Anna Duritskaya, a Ukrainian model.

Thousands of people attended a memorial service for the politician in Moscow last week and world leaders have urged Russia to track down the killers.

Miss Duritskaya did not see the murderer but spotted a getaway car driving away from the scene.

Ilya Yashin, an opposition .activist and friend of Mr Nemtsov, said of the detained men that it was “difficult to say whether these were the real executors [of the murder] or the investigation has been sent down the wrong track”, but he acknowledged that the security service apparently had some evidence to prove their guilt.

The two suspects could be formally arrested today.