Anti-capitalist protestors brought the city of Hamburg to a standstill on Friday as they fought running battles in the streets with police and tried to disrupt the G20 summit.

Protesters set upon police with iron bars and attacked a police helicopter with a firework which narrowly missed. They set cars alight across the city and tore down street signs to make their own barricades.

Melania Trump, the US First Lady, missed a boat trip laid on for the spouses of world leaders after the American delegation said it was unsafe for her to leave the building where she was staying.

At one point Malcolm Turnbull, the Australian prime minister, tweeted that he was under “security lockdown” with Joko Widodo, the Indonesian president.

Police guarding the hotel where Mr Turnbull and Vladimir Putin were both staying had earlier come under attack by protesters.