The United Nations Secretary-General, Antonio Guterres, has called for a de-escalation of the Russia-Ukraine crisis.

Guterres made the call in Wednesday's UN General Assembly plenary session on the situation in Ukraine's occupied eastern territories.

"It is time for restraint, reason and de-escalation," said the UN chief.

"There is no place for actions and statements that would take this dangerous situation over the abyss."

The session came two days after Russian President Vladimir Putin signed two decrees recognizing the "Luhansk People's Republic (LPR)" and the "Donetsk People's Republic (DPR)" as independent and sovereign states.

The move attracted condemnation from various states and international bodies.

NATO Secretary-General Jens Stoltenberg said Russia's move to recognize the two regions as independent "further undermines Ukraine's sovereignty and territorial integrity, erodes efforts towards a resolution of the conflict, and violates the Minsk Agreements, to which Russia is a party."