New York City's Columbia University has begun suspending students involved in a pro-Palestinian protest on campus after they defied a deadline to disperse.

College leaders earlier warned those who failed to disband from the two-week encampment by 14:00 EST (18:00 GMT) on Monday would face disciplinary action.

But as the deadline passed, dozens of students rallied at the site.

In Texas, police arrested dozens of protesters and dismantled their camp at the University of Texas at Austin.

Officials there said protesters had ignored directions to take down their tents.

The college said in a statement that "baseball-size rocks" had been found in the encampment and the "majority of protesters are believed to be unaffiliated with the university".

A lawyer who has worked with the protesters, George Lobb, told local media outlet KUT News that about 50 arrests had been made on Monday at the Austin campus. The BBC has contacted the university and local police for comment.

Similar demonstrations have taken place across the US since police cleared another camp at Columbia this month.

Pressure on the leadership of Columbia, an elite Ivy League university in Upper Manhattan, has been building to act or step aside.

"What continues to transpire at Columbia is an utter disgrace," US House of Representatives Speaker Mike Johnson wrote on X, formerly Twitter. "The campus is being overrun by antisemitic students and faculty alike."

The Louisiana Republican again called for the university's president, Nemat Shafik, to step down.

Earlier on Monday, a group of House Democrats urged Columbia's board of trustees to resign if it would not "act decisively, disband the encampment, and ensure the safety and security of all of its students".

"For the past week, this encampment has been the breeding ground for antisemitic attacks on Jewish students," the 21 lawmakers wrote. "The time for negotiation is over; the time for action is now."

Annual tuition and fees for Columbia add up to around $90,000 (£72,000) for undergraduates, making it one of the most expensive universities in the US.

Its campus has become the focal point of the country's debate over the war in Gaza and US support for Israel, as well as fears that antisemitism is putting Jewish students in danger.

On 18 April, police raided a pro-Palestinian encampment on the centre of campus and arrested more than 100 students.

But activists redoubled their efforts, regrouping into another encampment and prompting university leadership to move to hybrid learning.

Over the weekend, the university denied rumours of "an impending lockdown or evictions on campus" and told students it had no plans to bring back police "at this time".

How a police raid on Columbia protest ignited campus movement

On Monday morning, Dr Shafik said in a statement that "since Wednesday, a small group of academic leaders has been in constructive dialogues with student organizers to find a path that would result in the dismantling of the encampment".

"Regretfully, we were not able to come to an agreement," she said.

In a letter circulated to encampment organisers, the college warned it "will need to initiate disciplinary procedures because of a number of violations of university policies".

Students were instructed that if they voluntarily left the protest by 14:00 local time they would be allowed to complete their semesters.

Several hours after the deadline passed, the university's vice-president of public affairs said they had begun suspending students, temporarily barring them from campus, with those scheduled to graduate no longer eligible to do so.

University officials have said the suspensions are being imposed, in part, to avoid any disruption to graduation ceremonies on 15 May.

Columbia Students for Justice in Palestine, one of the main protest groups, vowed to defy the order in a post on X and called on activists to "protect the encampment".

As the afternoon deadline came and went, the cluster of tents on the Morningside campus remained in place.

Student supporters marched around the site, some banging drums and chanting: "Revolution!"

Mahmoud Khalil, one of the students who has been negotiating with Columbia officials, told the BBC that protesters believe it is "highly probable" that police will again be called in to clear the encampment.

"The students are here," added Mr Khalil, who said he was a Palestinian refugee who grew up in Syria. "They are holding their ground."

What do student protesters at US universities want?

Many wore face coverings, telling the BBC they were worried about being recognised and facing recrimination.

But the university wrote in its letter on Monday that it had already identified several participants.

Guarding them at the entrance of the encampment was a human chain of staff and faculty members in orange-and-yellow vests, locking arms with each other to prevent entry.

Meanwhile, police seen carrying zip ties and setting up barricades on campus remained on standby, apparently without any orders to make arrests or attempt evictions.

As Columbia administrators grapple with how to respond, the protest there has sparked similar demonstrations by students across the country.

The BBC is tracking protests or encampments on campuses in at least 22 other states and Washington DC.

Police at Virginia Tech arrested 91 people on trespassing charges on Sunday night, including 54 currently enrolled in the college.

Arrests were also made on Monday at the University of Georgia. At Cornell University in upstate New York, a "first set of immediate temporary suspensions" were given out on Monday, the college said in a statement.

At the University of California, Los Angeles (UCLA) tensions remained high after rival groups clashed when a barrier separating them was breached.

State troopers arrest a pro-Palestinian protester at the University of Texas at Austin

In her statement on Monday, Dr Shafik said that while Columbia plans to explore a range of ideas to address student concerns, it "will not divest from Israel".

At the same time, amid alleged incidents of hate speech, harassment and threats of violence by some participants, Jewish students have voiced concern about their safety on campus.

"The world is watching as you continue to fail your Jewish students," congresswoman Elise Stefanik, a New York Republican, said, as she accused Columbia of "empty threats and weak leadership".

Other Republicans, including former President Donald Trump, have highlighted antisemitic chants and incidents at the protests.

The White House is walking an increasingly fine line over the campus protests, seeking to balance the right to peaceful protest with condemnation of hateful speech.

"It is a painful moment, we get that," press secretary Karine Jean-Pierre said.

Declining to say how university leadership should act, she added: "Free expression has to be done within the law.” (BBC)

Update news