Iranian students defied authorities with protests for a third day on Monday, weeks after security forces crushed mass unrest with thousands killed and as the United States weighs possible air strikes against the Islamic Republic.

State media outlets reported students chanting anti-government slogans at Tehran University, burning flags at the all-women al-Zahra University, and scuffles at Amir Kabir University, all located in the capital.

Reuters also verified a video showing students at Al-Zahra University chanting slogans including “we’ll reclaim Iran”, but was not able to confirm when it was recorded.

In a new sign of the mounting tension in the Middle East, the United States began pulling non-essential personnel and family members from the embassy in Beirut, a senior State Department official said.

U.S. President Donald Trump has repeatedly threatened Iran since major nationwide protests across the country in January, saying on Thursday that “really bad things will happen” if talks between the countries fail to produce a deal.

Washington wants Iran to give up much of its nuclear programme, which it believes is aimed at building a bomb, limit the range of its missiles to short distances and stop supporting groups it backs in the Middle East.

It has built up forces across the Middle East, putting increased pressure on Iran as it weighs its response to U.S. demands amid ongoing talks.

Iranian Supreme Leader Ayatollah Ali Khamenei already faces the gravest crisis of his 36-year tenure, with an economy struggling under the weight of international sanctions and growing unrest that broke out into major protests in January.

On Sunday Iranian President Masoud Pezeshkian said negotiations with the U.S. had “yielded encouraging signals” even as a second U.S. aircraft carrier headed towards the Middle East.

Trump has not laid out in detail his thinking on any possible Iran strike. A senior White House official told Reuters last week there was still no “unified support” within the administration to go ahead with an attack.