Donald Trump has warned there 'could be big trouble' after Russia flew three fighter jets into neighbouring Estonia in a 'reckless' and 'brazen' attempt to intimidate the Baltic state.

The powerful MiG-31 warplanes spent 12 minutes violating Estonian airspace on Friday as they conducted combat operations to test the country's defences.

The move sparked an emergency response from Nato, which sent in F-35 fighters to intercept the Russian aggression.

There were also overnight strikes on Ukraine in which Volodymyr Zelensky said his country had been hit with a 'massive attack', killing at least three and injuring dozens.

In further provocation by Vladimir Putin, two Russian jets also made a show of force over a Polish oil platform in the Baltic Sea, breaching its safety zone.