China has joined Russia in opposing further Nato expansion as the two countries move closer together in the face of Western pressure.

Moscow and Beijing issued a statement showcasing their agreement on a raft of issues during a visit by Russia's Vladimir Putin for the Winter Olympics. Mr Putin claims Western powers are using the Nato defence alliance to undermine Russia.

It comes amid tensions over Ukraine, which he denies planning to invade. Some 100,000 Russian troops remain at the border with Ukraine, which is a former Soviet republic. Mr Putin, who has written that Russians and Ukrainians are "one nation", has demanded that Ukraine be barred from joining Nato. While the lengthy joint statement did not refer directly to Ukraine, the two countries accused Nato of espousing a Cold War ideology.

The talks, which the Kremlin said were "very warm", were held ahead of the Games opening ceremony. It was the first time the leaders have met face-to-face since the start of the pandemic. "Friendship between [Russia and China] has no limits, there are no 'forbidden' areas of cooperation,"

The exercises, involving ground troops and air forces, come amid growing instability in Afghanistan.

Chinese and Russian military forces are engaged in joint exercises in north-western China as ties grow between the two autocratic states amid uncertainty over instability in Afghanistan.

The exercises involving ground troops and air forces are due to continue through until Friday in the Ningxia Hui Autonomous region.

The region borders on Xinjiang, where China has detained more than one million Uyghurs and members of other Muslim minorities in what it calls a campaign against terrorism and extremism.

Xinjiang shares a narrow frontier with Afghanistan, and Beijing is concerned about violence spilling over its border if the Taliban take control in the country following the pullout of US and NATO troops.

While not part of a formal alliance, Russia and China have aligned their military and foreign policies largely in opposition to those of the US and its allies.

The official Xinhua News Agency said the exercises began on Monday and were presided over by Li Zuocheng, a member of the ruling Communist Party's Central Military Commission.

The exercise aims to "deepen the joint anti-terrorism operations between the Chinese and Russian militaries and demonstrate the firm determination and strength of the two countries to jointly safeguard international and regional security and stability", Xinhua said, citing Chinese and Russian officials.

"It reflects the new height of the China-Russia comprehensive strategic partnership of co-ordination for a new era and of the strategic mutual trust, pragmatic exchanges and co-ordination between the two countries," Xinhua said.

Russia has backed China in its claim to virtually the entire South China Sea, over which Beijing clashed with common rival the US at a high-level UN Security Council meeting on maritime security.

Beijing has been accused of sponsoring an attack on Microsoft Exchange email servers earlier this year which "recklessly" exposed thousands of businesses to criminal hackers.

The Chinese government has been accused of "systematic cyber sabotage" in statements by the UK and allies, including the US and Canada.

The allies are announcing that they believe Chinese state-sponsored hackers were responsible for an attack earlier this year which "indiscriminately" compromised an estimated 400,000 servers worldwide, leaving them exposed to criminals.

More than 70 organisations in the UK were compromised by the hack, perpetrated by a group associated with Beijing according to the National Cyber Security Centre. This attribution has been supported by allies.

Foreign Secretary Dominic Raab described the hacking campaign - which is believed to have compromised the on-premise email servers indiscriminately with an intention to subsequently target specific victims - as "a reckless but familiar pattern of behaviour" from the Chinese government.

The head of MI5 is to urge the public to be as vigilant about threats from "hostile states" as from terrorism. These include disruptive cyber-attacks, misinformation, espionage and interference in politics - and are usually linked to Russia and China.

In a speech on Wednesday, Ken McCallum will say these "less visible threats... have the potential to affect us all". He will say these threats are affecting UK jobs and public services and could even lead to a loss of life.

The head of the Security Service wants to challenge the idea that activity by so-called "hostile states", usually taken to mean primarily Russia and China, only affects governments or certain institutions. Instead, he will argue, in an annual threat update, that the British public are not immune to the "tentacles" of covert action by other states.