The girlfriend of Boris Nemtsov spoke publicly for the first time yesterday about the moment the opposition leader was shot dead as they crossed a bridge together near the Kremlin.

Anna Duritskaya, a Ukrainian model who had been with the former deputy prime minister and critic of President Putin for 2½ years, said that she never saw the killer and expressed dismay that the Russian authorities were refusing to let her go home to Kiev.

Speaking in a faltering voice drained of emotion, she told the online independent news channel Dozhd that she had noticed nothing suspicious over dinner in a restaurant overlooking Red Square late on Friday, or as they strolled downhill to the river, towards Mr Nemtsov’s home.

Then “on the bridge the murder happened”.

“I don’t want to answer questions about what happened on the bridge. I don’t want to talk about this,” she said. “I am in a very difficult psychological condition and I cannot talk about this any more now. I feel bad… I saw no one. I don’t know where he came from, [the killer] was behind my back.

“I turned around and all I saw was a light-coloured car. I saw neither the brand nor the licence plate of the car when it was driving away.”

Mr Nemtsov, 55, died almost instantly. Ms Duritskaya, who is more than 30 years younger than her partner, was taken away by police and interrogated without a lawyer.

“They questioned me until morning. I don’t remember where,” she said. “Some time later, several hours into the questioning, I asked to call a lawyer and the Ukrainian embassy consul.”

She said that she had given all the evidence she could yet was still kept under constant guard for several days.

However, a few hours after the interview appeared, Ms Duritskaya was allowed to leave Moscow and fly home to Ukraine. She will be a notable absentee at Mr Nemtsov’s funeral today, in common with Alexei Navalny, the jailed opposition leader, and Bogdan Borusewicz, the leader of the Polish Senate, who said last night that he had been denied entry to Russia.

Another mourner, the Latvian MEP Sandra Kalniete, was spending the night at a Moscow airport after immigration officials refused to let her into the country. Ms Kalniete, a former foreign minister, said she would fly back to Brussels today.

The British government will be represented at the funeral by the former prime minister Sir John Major.

There were conflicting reports yesterday as to whether the closed-circuit television cameras covering the site of the killing were working at the time of the attack. The business newspaper Kommersant, citing an anonymous interior ministry source, said that they were not, although the Moscow city authorities later said that the cameras were working and that there were others operated by federal security.

The newspaper said that investigators were sure that “the killers were not professionals”, that they used old ammunition and possibly an unreliable home-made weapon of the type used in 2006 to kill Anna Politkovskaya, the journalist and critic of the Kremlin.

The website Life News, which has close links to the security services, reported that the murderer was about 1.7m (5ft 7in) with short dark hair, wearing blue jeans and a brown sweater.

Late on Sunday, after tens of thousands of Russian protesters had shuffled through the drizzle to the spot where Mr Nemtsov was murdered, an unusual guest was invited on to Russian state television’s most popular weekly news and current affairs show.

Andrei Lugovoi, the prime suspect in the killing of Alexander Litvinenko, another critic of Mr Putin who was poisoned with polonium 210 in London in 2006, said that Mr Nemtsov’s murder was a carefully planned “provocation” organised by MI6 and other Western intelligence services.

Mr Lugovoi, a former KGB officer, is now a member of the State Duma, where he represents the ultra-nationalist LDPR. He told Russian TV that he was “convinced that preparations for killing Nemtsov began at least a year ago as part of a strategic plan [aiming for a] strategic outcome in Russia linked to Ukraine”.

“This may not be the end, but the beginning of provocations,” he warned viewers. “It is all part of a geopolitical game of western intelligence services.”

No explanation was given for Mr Lugovoi’s presence on the show and there was no mention of evidence allegedly linking him to Mr Litvinenko’s death. His place was later taken in the 145-minute-long panel discussion programme by Vladimir Zhirinovsky, the head of the LDPR, who recently suggested attacking Kiev with napalm.

Many leading figures from the Moscow intelligentsia had refused to appear on Sunday’s show. “Close friends and associates who knew Boris Nemtsov well were being called all day Saturday by researchers from the show, but none of them agreed to go on it,” a source told The Times, adding that they considered the programme a propaganda mouthpiece for Kremlin-approved views.

In Geneva yesterday Sergei Lavrov, the foreign minister, promised that the murder would be “fully investigated”, although he added that any “attempt to use the heinous killing of Boris Nemtsov for political purposes is despicable”.