Scared for her life: Model Anna Duritskaya, 23, is under police protection in Ukraine after reporting a 'threat to her life from unidentified individuals' Ukraine has put the girlfriend of slain Russian opposition politician Boris Nemtsov under state protection after she received death threats. Model Anna Duritskaya, 23, is now under the guard of SBU secret services and the police. Kiev also said today that she would not return to Moscow over the probe into the death of the Vladimir Putin foe. 'We will not let her go back to Russia,' said Anton Geraschenko, an aide to the Interior Minister. 'If Russian investigators need to talk to her, they will have to come to Ukraine.' The announcement came as another of Russia's leading opposition figures vowed that he and his supporters will not be intimidated by as he walked free from a 15-day spell in jail. Alexei Navalny, who had been convicted of handing out leaflets calling for an opposition rally, said he would continue his staunch criticism of Vladimir Putin's government despite the Mr Nemtsov's murder seven days ago. Emerging unshaven from a Moscow detention centre this morning, Mr Navalny said: 'This act of terror hasn't achieved its goal, it will not frighten me or my comrades. We will not reduce our efforts, we will not step back.' A key figure in Boris Yeltsin's 1990s government, Mr Nemtsov was the most prominent figure in Russia's liberal opposition to be killed during President Vladimir Putin's 15-year rule. The 55-year-old was shot four times in the back by a gunman in a passing car as he walked hand-in-hand with Miss Duritskaya on a bridge across the Moskva River on Friday night, in the shadow of central Moscow's St Basil Cathedral. The Ukrainian woman - physically unhurt in the attack - revealed the death threats to police in Kiev, who said today they were providing her with protection. 'On March 5, Anna Duritskaya, who is a witness in the case in the murder of Russian opposition politician Boris Nemtsov, turned to the Ukrainian police in the Kiev Region with a statement on a threat to her life from unidentified individuals,' said the prosecutor-general's office in Ukraine. The statement offered no information on who might have issued the threats, according to the Associated Press. The model was staying with her parents since returning to her home country. A relative in Ukraine said she was 'in a bad mental state'. In the aftermath of Mr Nemtsov's assassination, Miss Duritskaya was repeatedly questioned by Russian investigators, and she complained that she was held under armed guard and unable to leave the country. However, she returned to Ukraine last week. 'This act of terror will not frighten me or my comrades': Opposition leader Alexei Navalny said he would continue his staunch criticism of Vladimir Putin's government despite the Mr Nemtsov's murder . Gunned down: Boris Nemtsov, 55, (left) and 23-year-old Miss Duritskaya (right) were walking hand-in-hand through Moscow after having dinner on Friday night when he was shot four times in the back . As thousands gathered in Moscow to pay their last respects at Mr Nemtsov's funeral, Putin insisted the Russian law enforcement authorities would do 'everything' to solve the crime. However, Nemtsov's eldest child, Zhanna Nemtsova, 30, revealed that investigators had not spoken to a single member of his close family six days after the murder. They believe his 'cruel and barefaced murder' was because of his political opposition to the Kremlin. Yesterday a top Nato official suggested Putin was responsible for Mr Nemtsov's death as he accused the Russian president of silencing dissent at home while seeking to turn Ukraine into a failed state. 'We've seen that the victims are not just in eastern Ukraine, with the brutal murder of Boris Nemtsov last Friday,' NATO Deputy Secretary General Alexander Vershbow said. Speaking to members of parliament from EU countries at a conference in Riga, Mr Vershbow went on: 'While we don't know who pulled the trigger, we do know that Boris Nemtsov was a powerful voice for democracy and against Russia's involvement in Ukraine ... (and) was among those vilified as "traitors" and "fifth columnists" in Russia's official propaganda.' 'We will not let her go back to Russia': Anton Geraschenko, an aide to Ukraine's Interior Minister, said Miss Duritskaya would not return to Moscow over the probe into the death of the Vladimir Putin foe . Honoured: People  applaud as workers carry the coffin of Kremlin critic Boris Nemtsov during a ceremony at the Sakharov centre in Moscow, where his body was laid in state after he was shot dead on Friday . Mr Nemtsov, a father of four, first gained an international profile after being spotted by former British Prime Minister Margaret Thatcher as a future leader of Russia. He was Russia's deputy prime minister from 1997 to 1998 during Boris Yeltsin's presidency, but found himself on the fringes of the country's politics after a tanking economy forced Yeltsin's resignation. The politician founded a number of opposition movements after leaving the Russian parliament in 2003 and he had served as the co-chair of the opposition Republican Party of Russia - People's Freedom Party since 2012. It has been reported that Nemtsov angered Putin's government two years ago when he charged that billions of dollars had been stolen from funds designated for the 2014 Winter Olympics in Sochi, his hometown. In January 2011, he was sentenced to 15 days in jail after being arrested at a New Year's Eve protest rally for 'disobedience towards police'. Murder: Flowers lie at the scene of Mr Nemtsov's murder, while police divers search the Moskva River for the gun that was used to gun him down. He was a key figure in Russia's liberal, pro-West opposition . Pro-West in his ideology, Mr Nemtsov had told U.S. diplomats he wanted to take Russia on a pro-EU, pro-Nato course, including eventual membership of both organisations, according to a diplomatic cable released by Wikileaks. 'The key, Nemtsov argued, was to present this strategy as the only viable choice for Russia,' wrote a U.S. embassy attaché in the note dated February 2006. But, the diplomat continued, 'Nemtsov also realizes that his association with the Yeltsin era will probably limit support for any initiative with his name on it, and he is counting on the next generation of politicians to carry the liberal banner.' Putin has claimed Mr Nemtsov's murder - yards from the Kremlin - was a 'provocation'.
Anna Duritskaya, 23, told police she had received anonymous threats . She was with Boris Nemtsov, 55, when he was gunned down in Moscow . Now back in Ukraine, she had complained she was being held in Russia . Nemtsov family reveals they have had no contact from murder detectives .