Xi was the first leader to meet the Russian president since the ICC issued an arrest warrant for him over the deportation of Ukrainian children to Russia during its year-old invasion of Ukraine.

The visit triggered an angry reaction from Ukraine, with a presidential aide blasting its 'cynicism' and 'lack of remorse'.

The trip will be closely watched in Western capitals for signs Xi may push for peace talks between Moscow and Kyiv.

Putin's surprise visit to Crimea was his first to the peninsula since he sent troops to Ukraine on Feb 24 last year, apart from when he drove across the bridge linking the territory to mainland Russia last December.

The arrest warrant for Putin, a sitting head of state of a UN Security Council member, is an unprecedented step for the ICC.

According to Kyiv, 16,221 Ukrainian children had been deported to Russia as of last month.

The US says the incident shows Russia is behaving irresponsibly in international airspace, while Moscow accused Washington of trying to escalate tensions near Crimea.

Mikhail Abdalkin was convicted for a stunt, which he filmed and posted on social media, based on a Russian saying that someone who has been strung along or deceived has had noodles hung on their ears.

Sending any fighter jets would mark a crucial development in the conflict and would boost Kyiv's defence against Russian missile strikes and drone attacks.

Relations are at their lowest point in decades over Moscow's invasion of Ukraine.

Several times before the collision, the Russian fighter jets dumped fuel on the MQ-9, possibly trying to blind or damage it, and flew in front of the unmanned drone in unsafe manoeuvres, the US military says.

Russia's state news agency says so far none of the involved sides has indicated a withdrawal.