Footage shows clashes between police and anti-Israel protesters at Columbia University in New York on April 30.

Demonstrators had barricaded themselves into Hamilton Hall and chanted 'We shall not be moved' as officers advanced towards the entrance.

NYPD Deputy Commissioner of Public Information Tarik Sheppard said that many of the protesters were not university students but rather outside agitators.

He described them as 'professionals' who travel across the country for such demonstrations, often influencing passionate but impressionable students.

Israel has blitzed the Gaza Strip in retaliation for an attack by the governing party Hamas on a Jewish music festival On 7 October last year.

However, the situation - which Israel claims is self-defence - has attracted criticism from around the world.

Craig Mokhiber, a director at the United Nations, has resigned over the organization's 'failure' to act against what he called a 'text-book case of genocide' by Israel against Gaza.