Washington DC - President Joe Biden opposes the seizure of a Columbia University campus building by pro-Palestinian protesters, the White House said Tuesday as Gaza demonstrations raged at colleges across the country.

"The president believes that forcibly taking over a building on campus is absolutely the wrong approach," National Security Council spokesman John Kirby told an online briefing.

"That is not an example of peaceful protest."

Masked demonstrators smashed windows and entered the Hamilton Hall building at the Ivy League university in New York, barricading themselves inside with metal tables.

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The university has become the focal point for Gaza protests around the United States.

"You just got to do it peacefully. You can't hurt anybody, and you can't... be disrupting the educational pursuit of your fellow students," Kirby said.

The White House was "watching these protests with concern," although it had no evidence of "bad actors" trying to take advantage of the demonstrations, Kirby added.

While Biden was "mindful of the strong feelings" of demonstrators, it would not change his support for Israel's offensive against Hamas in Gaza, the spokesman said.

"The president also has... a responsibility to look after our national security interests around the world and and that also means making decisions in the region that support those interests," he added.