Moscow was ready to put its nuclear forces on alert to ensure Russia's annexation of Crimea from Ukraine last year, President Vladimir Putin said in a pre-recorded documentary aired on Sunday.

Putin also said that Russia had saved the life of Ukraine's former pro-Moscow president, Viktor Yanukovich, who he said had been in danger after 'revolutionaries' seized power following weeks of violent street protests in Kiev last year.

"For us it became clear and we received information that there were plans not only for his capture, but, preferably for those who carried out the coup, but also for his physical elimination. As one famous historical figure said: 'No person, no problem'," Putin said.

Protests over Yanukovich's decision to back away from a trade agreement with the European Union in favour of closer ties with Moscow forced him from power in February last year. Yanukovich's overthrow ultimately prompted Russia to seize and annex the Black Sea peninsula of Crimea.

"Of course it wasn't immediately understandable (what the reaction would be to Crimea's annexation). Therefore, in the first stages, I had to orient our armed forces. Not just orient, but give direct orders," he said.

When asked if he had been ready to put Russia's nuclear forces on alert, he said: "We were ready to do it."

OUT OF PUBLIC VIEW

Putin has not been seen in public or on live television since March 5, prompting a wave of savage mockery across the Internet, despite official insistence that it was business as usual in the Kremlin.

The independent news broadcaster Dozhd said the Kremlin had declined to comment on its report that Putin had not been in Moscow but in Novgorod province, at his Lake Valdai residence, for the last several days. An Austrian newspaper reported that Putin was suffering from back problems, and that a Viennese orthopaedic expert had travelled to Russia to treat him.

The film, shown across Russia ahead of the first anniversary of Russia's annexation of Crimea, documented the seizure of the peninsula and provided details of Yanukovich's last hours in Ukraine before he fled to Rostov-on-Don, in southern Russia.

Putin said Yanukovich had called on Feb. 21 last year to lay out plans to leave the capital, where violent street protests had been raging for weeks.

"I told him my point of view that, in such a situation, it's best not to leave the capital," said Putin.

From Kiev, Yanukovich travelled to Kharkiv, then on to Donetsk, where he called Putin to ask for help.

Putin suggested meeting him personally in Rostov-on-Don, but Yanukovich's plane was not given permission to leave. He then travelled to Crimea, from where he was spirited to Russia.