Russian President Vladimir Putin has ordered troops into separatist-held parts of eastern Ukraine in what the Kremlin called a "peacekeeping" mission, just hours after he signed decrees recognizing the independence of the Moscow-backed regions.

It is unclear if Russian troop movements marked the beginning of an invasion of Ukraine that Western leaders have warned about for weeks. But multiple US and Western officials warned Monday's move could serve as the opening salvo of a larger military operation targeting the country.

In a fiery speech on Monday night, Putin blasted Kyiv's growing security ties with the West, and in lengthy remarks about the history of the USSR and the formation of the Ukrainian Socialist Soviet Republic, appeared to cast doubt on Ukraine's right to self-determination.

"Ukraine has never had traditions of its own statehood," he said, calling the eastern part of the country "ancient Russian lands."

The decrees signed by Putin conveyed Moscow's official recognition over two breakaway territories in the Donbas region of eastern Ukraine -- the Donetsk People's Republic and Luhansk People's Republic (DPR and LPR). The decrees recognized them as independent states, and guaranteed their security with Russian troops. The decrees said that Russian so-called peacekeeping forces would be deployed in the regions.

A senior US administration official said the speech was meant to "justify war" to the Russian people and that it amounted to "an attack on the very idea of a sovereign and independent Ukraine" using "a number of false claims" meant to justify military action.

"The human costs of a further Russian invasion and occupation will be devastating," the official said.

Separatists in eastern Ukraine have long had substantial backing from the Kremlin, with the US, NATO and Ukrainian officials saying Moscow supplies them with advisory support and intelligence, and embeds its own officers in their ranks. Russia has always denied having its own troops on the ground.

Moscow has also distributed hundreds of thousands of Russian passports to people in Donbas in recent years, with Putin attempting to establish facts on the ground by naturalizing Ukrainians as Russian citizens. Kyiv and the West maintain that the region is part of Ukrainian territory, although the Ukranian government asserts the two regions have been in effect Russian-occupied since 2014, when the conflict in eastern Ukraine began.

On Monday, US Secretary of State Antony Blinken called Putin's decision to recognize the breakaway regions "a clear attack on Ukraine's sovereignty" and said US President Joe Biden would sign an executive order prohibiting "all new investment, trade and financing by US persons to, from, and in the so-called 'Donetsk and Luhansk People's Republics."

Biden said last month that "if any assembled Russian units move across Ukrainian border, that is an invasion. But it will be met with severe and coordinated economic response that I've discussed in detail with our allies, as well as laid out very clearly for President Putin."

Earlier on Monday, Putin held a highly choreographed televised meeting with his top officials, accusing Kyiv of carrying out acts of aggression.

Putin also accused the West of threats and blackmail during the previously unscheduled convening of the Russian security council that, in unusually theatrical setting, was shown on television.

The broadcast airedjust hours after the White House announced that US President Joe Biden agreed "in principle" to French-brokered talks with Putin as long as Russia does not further invade Ukraine. The Kremlin said earlier on Monday that there were "no concrete plans" for a meeting.

Speaking about the possibility of talks with Biden, Putin -- who held two lengthy phone calls with the French President Emmanuel Macron on Sunday -- hinted he was skeptical.

"Yesterday I spoke with the French President on two occasions, with the second call lasting until 2:00 a.m. or so. He assured me that the American position has changed somewhat. But when I asked what these changes are, he, unfortunately, could not say." Putin said.

He then referred to remarks made on Sunday by Blinken, who stressed once again that the issue of Ukraine's membership in NATO is "an issue for Ukraine and for NATO."

Assurances that Ukraine would not be admitted to NATO in the future are one of the central demands made by the Kremlin.

With his top officials assembled in front of him at the extraordinary meeting of the security council, Putin appeared following claims made by the Russian military earlier on Monday that troops and border guards engaged in a clash with a "sabotage and reconnaissance group from the territory of Ukraine" inside Russian territory.

"Russia has always tried to resolve all conflicts by peaceful means. Nevertheless, the Kyiv authorities conducted two punitive operations in these territories [Donetsk and Luhansk], and it seems that we are now witnessing an escalation for the third time," Putin said, without further elaborating or providing specifics.

CNN has not independently verified reports of a clash inside Russia's territory. Ukrainian Foreign Minister Dmytro Kuleba denied a clash occurred, saying on Twitter, "I categorically refute the disinformation of the Russian Federation."

Kuleba said Ukraine "did not attack Donetsk, Luhansk, did not send saboteurs or armored personnel carriers across the border, did not fire on the territory of the Russian Federation or the checkpoint at the border, did not commit sabotage, does not plan such actions."

The increase in combative language from Putin came as tensions grew once again in eastern Ukraine.

Ukraine's Joint Forces Operation said it recorded 32 ceasefire violations as of 4 p.m. local time, a number that was roughly in line with those over the weekend.

New satellite images showed intensified activity among Russian units close to Ukraine's north-eastern border and the Ukrainian Defense ministry said it recorded dozens of ceasefire violations on Sunday.

Defense minister Oleksii Reznikov said Monday that Ukraine was not seeing any withdrawal of Russian forces from positions close to the border.

And in a further escalation, Belarusian officials announced Sunday that joint Russian military exercises in Belarus that were slated to end over the weekend would continue, implying that Russian forces may extend their stay.

CNN's Nathan Hodge, Anna Chernova, Kevin Liptak, Josh Pennington, Sarah Dean and Amy Cassidy contributed to this report.