Nato also said it would stand with Ukraine for as long as necessary.

This comes after at least 19 people were killed and scores more injured, as Russian missiles hit regions across Ukraine, including central Kyiv.

Strikes continued on Tuesday, with civilians advised to stay in air raid shelters.

Russian President Vladimir Putin said the attacks were in retaliation for a strike on a key bridge linking Russia with occupied Crimea, for which he blamed Ukraine even though Ukraine didn't claim responsibility.

Western leaders were quick to condemn the Russian escalation, and the G7 on Tuesday reiterated its commitment to Ukraine.

"We will continue to provide financial, humanitarian, military, diplomatic and legal support and will stand firmly with Ukraine for as long as it takes," the group said in a statement.

The bloc also condemned Putin's recent attempts to annex four regions of Ukraine with self-styled referendums.

Ukrainian President Volodymyr Zelensky asked the G7 for further air defence capabilities.

He also asked the alliance to support an international mission on the Ukraine-Belarus border after Belarusian leader Alexander Lukashenko - a close ally of Mr Putin - agreed to deploy forces with Russian soldiers at the border with Ukraine.

Nato Secretary General Jens Stoltenberg said the military bloc would also continue to stand by Ukraine.

In a press conference, Mr Stoltenberg suggested that Nato needed to produce more weapons, and added that any attack on infrastructure critical to Nato would trigger a "united and determined response". It comes two weeks after a series of attacks on the Nord Stream gas pipelines, which many Western leaders indirectly suggested may have been caused by Russia.

In its statement the G7 said is was "deeply troubled" by these attacks, and welcomed further investigation into what caused them.