China has criticised "indiscriminate" sanctions against Chinese companies and taken aim at Nato as the war in Ukraine enters its third year.

Zhang Jun, China's permanent representative to the United Nations, said on Friday that Beijing "firmly opposed" the "unlawful sanctions" imposed on Chinese companies by the United States, Britain and the European Union, "using the Ukraine issue as an excuse".

Zhang said the situation Europe was facing today was closely related to the eastward expansion of Nato since the end of the Cold War and, without naming Secretary General Jens Stoltenberg directly, also attacked the "head of Nato".

He also said China wanted to play a constructive role and was working towards a political settlement.

"We encourage Nato to do some soul-searching, come out of the cage of Cold War mentality, and refrain from acting as an agent of trouble instigating bloc confrontation," Zhang said in his most blunt criticism of the alliance yet.

"We urge the head of Nato to look at the world through an objective lens, stop sabre-rattling, and do things that are genuinely conducive to world peace.

"China played no part in the creation of the Ukraine crisis, nor is China a party to the crisis itself. We have not been watching the fire from across the river, much less cashing in on the crisis."

Recently, Stoltenberg, who will step down from the role shortly, has made several comments that China was closely watching the war in Ukraine, drawing parallels with Taiwan that Beijing has fiercely resisted.

In one such comment he told Reuters: "Today it is Ukraine, tomorrow it can be in Taiwan. So Beijing, China is watching closely what's going on in Ukraine."

Beijing views Taiwan as a breakaway province to be reunified with the mainland, by force if necessary. Most countries, including the US and European Union members, do not recognise Taiwan as an independent state, but oppose any attempt to take the island by force.

Zhang also criticised the sanctions, telling a meeting of the Security Council: "Certain countries, using the Ukraine crisis as a pretext, have indiscriminately imposed unilateral sanctions and long-arm jurisdiction and exerted unjustified pressure on the businesses of other countries, which has adversely impacted the global industrial and supply chains and disrupted the order of global trade.

"China will continue to take necessary measures to safeguard the legitimate rights and interests of Chinese enterprises and citizens."

During the Friday meeting, Zhang also repeated China's calls for a political settlement, urging "relevant parties" stop supplying weapons and "stoking the fire".

On Wednesday the European Union blacklisted three mainland Chinese and one Hong Kong companies that were accused of helping Russian buyers access goods with dual military and civilian uses.

The following day three Chinese firms were also sanctioned by Britain for allegedly supporting the conflict and on Friday the United States sanctioned 17 firms from mainland China and Hong Kong.

Beijing has repeatedly denied accusations that Chinese companies have been supplying weapons and other equipment to help Russia's war effort.

A Group of 7 leaders' joint statement released on Saturday expressed concerns about transfers to Russia from businesses in China of dual-use materials and components for weapons and military production.

Beijing has not condemned Russia's invasion and denied accusations that it is considering arming Russia. It has also stressed it is neutral and wants to play a constructive role in mediating the crisis.

However, that has not been enough to convince Western countries, which have urged Beijing to put more pressure on Russia to stop the war.

Russia and China announced a "no-limits" partnership days ahead of the Russian invasion of Ukraine two years ago and the two countries have increased their political and economic links since then.