In comments in a documentary aired on state TV on Sunday, Mr Putin said the life of ex-Ukrainian leader Viktor Yanukovych had been in danger.

He also said Russians in Crimea were in danger before Russia annexed it.

In a previously released clip from the film, he said he ordered the annexation weeks before a referendum was held.

Crimea was formally absorbed into Russia on 18 March, to international condemnation, after unidentified gunmen took over the peninsula.

The documentary aired amid speculation over Mr Putin's whereabouts with the Russian leader having not been seen in public since 5 March.

The Kremlin has denied rumours that the president might be sick or even dead and says Mr Putin will meet his Kyrgyz counterpart, Almazbek Atambayev, on Monday.

'Our historical territory'

Speaking on the documentary - called The Path To The Motherland - Mr Putin said: "We never thought about severing Crimea from Ukraine until the moment that these events began, the government overthrow".

On putting Russia's nuclear weapons into a state of combat readiness, Mr Putin said: "We were ready to do this."

"[Crimea] is our historical territory. Russian people live there. They were in danger. We cannot abandon them," he added.

He said he used a "closed opinion poll" of Crimeans to judge whether they wanted to remain in Ukraine and found that "75% of the general population desired to join Russia". No details of how the survey was conducted were given by Mr Putin.

Russia initially denied that soldiers who appeared in Crimea without military insignia on their fatigues - dubbed the "little green men" - were Russian.

But Mr Putin subsequently admitted deploying troops on the peninsula to "stand behind Crimea's self-defence forces".

The formal annexation of Crimea sparked unrest in eastern Ukraine in April, when pro-Russian protesters occupied government buildings in Donetsk, Luhansk and Kharkiv demanding independence.

A month later, pro-Russian separatists in Donetsk and Luhansk declared independence from Ukraine after unrecognised referendums.

Ukraine responded by launching an "anti-terrorist operation" against them and the region became engulfed in a conflict which has cost at least 6,000 lives, according to the UN.

(BBC)