NEW YORK: A major conflict between Russia and Ukraine must be prevented at all costs, UN Under-Secretary-General for Political and Peacebuilding Affairs Rosemary DiCarlo has told an emergency session of the Security Council.

Briefing the council late on Monday, DiCarlo voiced concern over the intensifying shelling in Donetsk and Luhansk which followed Russian President Vladimir Putin’s decision to send Russian troops into the two separatist pro-Moscow regions in the east of the country.

Artillery fire has led to a number of casualties, as well as the targeting of civilian infrastructure and mass evacuations.

Reminding Security Council members of their responsibilities under international humanitarian law, DiCarlo called for an immediate halt to hostilities, the protection of civilians and civilian infrastructure, and an end to inflammatory rhetoric.

The UN official described the coming hours and days as “critical,” and reiterated the UN’s commitment “to stay and deliver, and remain fully operational in Ukraine, including in the Donetsk and Luhansk regions.”

Russia’s troop deployment into eastern Ukraine followed a decision to recognize the breakaway Donetsk and Luhansk regions as independent states.

Describing the deployment as a “peacekeeping mission,” Putin said that the move should have been made “a long time ago.”

After the announcement, Ukraine requested an urgent meeting of the Security Council, presided over by Russia this month.

The conflict in eastern Ukraine, now in its eighth year, has left more than 3.4 million Ukrainians in need of urgent humanitarian aid, according to the UN.

Ukrainian Ambassador Sergei Kyslystya described Russia as a “virus” spread by the Kremlin, making the UN “sick.”

He said Ukraine’s internationally recognized borders are unchangeable regardless of Russian actions and statements.

“We are on our land. We owe nothing to anyone. And we will not give away anything to anyone. We are not afraid of anything or anyone.”

US Permanent Representative to the UN Linda Thomas-Greenfield warned of “swift and severe” consequences should Russia invade Ukraine.

She said Putin “is testing our resolve” and accused the Russian leader of wanting to “demonstrate that through force, he can make a farce of the UN.”

Thomas-Greenfield began her address by recalling the Second World War, saying that the ensuing UN charter has “stood as a bulwark against the worst impulses of empires and autocrats.”

She added: “History tells us that looking the other way in the face of such hostility will be a far more costly path. Russia’s clear attack on Ukraine’s sovereignty and territorial integrity is unprovoked. It is an attack on Ukraine’s status as a UN member state. It violates a basic principle of international law and it defies our charter.”

The US envoy accused Putin of seeking to create a pretext for a further invasion of Ukraine.

“The consequences of this action will be felt far beyond Ukraine’s borders,” she said.

Thomas-Greenfield added: “In this moment, no one can stand on the sidelines.”

UK Permanent Representative Barbara Woodward said: “Russia has brought us to the brink. We urge Russia to step back.”

She urged the Security Council to defend the territorial integrity of Ukraine and stay united in condemning “aggression against a sovereign nation.”

However, Russia’s Permanent Representative Vassily Nebenzia, who was presiding over the emergency meeting, dismissed what he called “a number of very emotional statements, categorical assessments and far-reaching conclusions.”

He urged Western envoys to “come to their senses, put aside their emotions and not make the situation worse.”

Nebenzia cited agreements “signed today by Luhansk and Donetsk People’s Republic,” reiterating that “maintaining peace in their territories will be carried out by the armed forces of the Russian Federation.”

UN Secretary-General Antonio Guterres expressed concern over Russia’s recognition of Donetsk and Luhansk as independent states.

He described Russia’s troop deployment as “a violation of the territorial integrity and sovereignty of Ukraine and inconsistent with the principles of the charter of the United Nations.”

Guterres called for “the peaceful settlement of the conflict in accordance with the Minsk Agreements, as endorsed by the Security Council in resolution 2202.”