Russia has developed a new cruise missile that is invincible, according to President Vladimir Putin.
Mr Putin made the revelation as he laid out his key policies for a fourth presidential term, ahead of an election he is expected to win in 17 days' time.
He showcased a range of new weapons, including the cruise missile that could "reach anywhere in the world".
Using video presentations, he said the missile could not be stopped by the US shield in Europe and Asia.
It was "a low-flying, difficult-to-spot cruise missile with a nuclear payload with a practically unlimited range and an unpredictable flight path, which can bypass lines of interception and is invincible in the face of all existing and future systems of both missile defence and air defence".
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Another weapon he discussed was a submarine launched, long-range missile capable of delivering a nuclear warhead.
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During the two-hour televised speech to a joint sitting of both houses of parliament, he encouraged Russians to suggest names for the two systems. He argued that Russia had reacted after years of pleading with the US not to break away from anti-missile treaties.
Opposition leader barred from vote
Mr Putin faces seven challengers on 18 March, although none is expected to attract widespread support. The president played no part in a raucous televised debate broadcast on Wednesday that featured the other candidates.
Absent from the campaign is prominent opposition leader Alexei Navalny, who has been barred from running and has called on voters to boycott the poll.
President Putin has so far done little campaigning, and until now said little about his plans for the next six years.
How credible are these claims?
Analysis by Jonathan Marcus, BBC defence correspondent
Media captionMr Putin demonstrated the new weaponry in a series of videos
President Putin's emphasis on a strong Russia modernising its nuclear arsenal is a reflection of similar statements over recent months from his US counterpart Donald Trump.
In his remarks, Mr Putin highlighted the development of two new nuclear delivery systems, which, he said, could evade US anti-ballistic missile defences.
This is essentially because neither of them are ballistic missiles, which are fired out of the atmosphere in a high-arcing trajectory.
One - effectively a very long-range nuclear-tipped torpedo - has been rumoured to be under development since Soviet days but is now seen by US analysts as a credible theat.
The second system - described by Mr Putin as a cruise missile - looks to be more of a work in progress and may be a kind of very high-speed "hypersonic" system - described by one arms control expert as a "glider on steroids" - that again could evade existing anti-missile defences.
China and the US are also working on similar systems of their own.
Fighting poverty
In the first half of his speech, he pledged to halve poverty in the country within the next six years.
"Every person matters to us," he said, adding that he wanted to increase employment and longevity.
He said he wanted Russia to emulate life-expectancy rates in Japan and France.
In 2000 there were 42 million people in Russia living below the poverty line, he noted; today there were 20 million, but this still needed to come down.
He warned Russians not to take the country's power for granted.
"We have no right to allow the stability we have achieved to lead to complacency. Especially since we are far from resolving many problems," he said.
"Russia is now a leading country with a powerful foreign economic and defence potential. But from the point of view of the extremely important task of ensuring people's quality of life and welfare we, of course, have not achieved the level we require. But we have to do this and will do this," he added to applause.
Defence and territory
Russia's military power was built to maintain peace in the world, he argued. However, if anyone fired a nuclear weapon against Russia, he said it would be met with instantaneous retaliation.
Last month, the US proposed diversifying its nuclear arsenal and developing new, smaller atomic bombs, largely to counter Russia.
Russia's foreign minister called the move "confrontational".
In Thursday's speech, Mr Putin also spoke of Russian operations in Syria - supporting the Assad government's fight against rebels - which, he said, showed off the country's increased defence capabilities.
Russia recently sent two of its most advanced fighter planes, Su-57s, to Syria, even though they are still undergoing tests.
Image copyrightAFP
Image caption
There was no confirmation that Russia's new stealth fighters have been used in combat in Syria
Mr Putin also announced that a bridge to the Crimean peninsula would be open within the next couple of months. Russia annexed Crimea from Ukraine in 2014, during Mr Putin's current term in office.
Russia was safeguarding its interest in the Arctic region by strengthening its military infrastructure in the region, he said.
Technological growth
Digital growth was also essential, Mr Putin said. He said he wanted Russia to become one of the world's main hubs for storing and processing big data.
Image copyrightEPA
Image caption
Graphics -including this one on Russia's working-age population (in millions) - flashed up throughout
He called for more progress in making robots and artificial intelligence. New talent in technology should be nurtured and foreigners should be encouraged to study in Russia, he said.
All government business would be digitalised "to make it more transparent to fight corruption", he said.
"Most government officials are good, result-orientated people," he added, "but these plans will help everyone."
Ordinary concerns
The first part of the speech was tailored towards working Russians and their concerns.
Mr Putin pledged to spend more on roads and reduce accidents. He said teachers deserved good salaries and wages, and there should be better access to medical services for people in remote areas.
He also said internet access would be provided to rural populations across the country, "from the far east to the Siberian north".