NATO, the world's largest and most powerful military alliance, has branded Russia the biggest "direct threat" to Western security after its invasion of Ukraine.

World leaders have been meeting in Spain, with conversations centred around the Kremlin's invasion, and Beijing's growing international ambitions.

As part of the two-day summit, a new strategic concept was put forward that sets the alliance's areas of focus and is updated roughly once a decade.

Here's what you might have missed.

NATO backs military aid for 'heroic' Ukraine

NATO has agreed to plans to modernise Kyiv's beleaguered armed forces, saying it stood fully behind Ukrainians' "heroic defence of their country".

US President Joe Biden announced more land, sea and air force deployments across Europe from Spain in the west to Romania and Poland bordering Ukraine.

Meanwhile, Britain said it would provide another 1 billion pounds ($1.7 billion) of military support, including air defence systems, uncrewed aerial vehicles and new electronic warfare equipment. 

In a nod to the deterioration in relations with Russia since the invasion, a NATO communique also labelled Russia the "most significant and direct threat to the allies' security".

Russia sends its own warning

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As world leaders met, Russian President Vladimir Putin fired his own salvo, warning Finland and Sweden that if they welcome NATO troops and military infrastructure onto their territory, Russia would respond in kind.

The two formerly non-aligned Baltic countries were formally invited Wednesday to join the Western military alliance.

Mr Putin said that Russia will have to "create the same threats for the territory from which threats against us are created."

NATO 'clear-eyed' about 'serious challenges' China presents

For the first time, Beijing was mentioned in NATO's strategic concept, which sets the alliance's areas of focus.

It said China's "stated ambitions and coercive policies challenge our interests, security and values", and accused the nation of using malicious hybrid and cyber operations, confrontational rhetoric and disinformation to target NATO allies and harm NATO's security.

China denies any such tactics.

The document also touches upon China's economic ambitions, stating Beijing was seeking to control key technological and industrial sectors, critical infrastructure, and strategic materials and supply chains.

"China is not our adversary but we must be clear-eyed about the serious challenges it represents."

ABC/wires