Yemen's powerful Shiite militia blocked access to Sanaa University on Monday as opponents to their takeover of the capital called for more demonstrations against their tightening grip on Sanaa.
The militiamen, known as Huthis, set up barriers along roads leading to Change Square just outside the university, a hotbed of opposition, witnesses and activists said.
Opponents to the Huthis have urged more demonstrations on Monday against their occupation of the capital, which has plunged Yemen into a deepening crisis.
Western-backed President Abdrabuh Mansur Hadi, a key US ally in the fight against Al-Qaeda, tendered his resignation last week after the Huthis kidnapped his chief of staff and seized key buildings.
Yemen's parliament on Sunday again postponed a session to consider Hadi's resignation, extending a dangerous power vacuum.
The militia, who descended from their base in Yemen's rugged north to overrun the capital in September, fired in the air on Sunday to disperse a protest at Change Square.
The Huthis detained several activists and two reporters from local media at the protest, but the journalists were released after signing pledges not to cover demonstrations, according to an activist, Mohammed al-Saadi.
Four political parties negotiating with the Huthis to bring the country out of crisis meanwhile announced late Sunday they were ending contact with the militia.
Abdullah Noaman, head of the Nasserist Unionist People's party, accused the Huthis of "arrogance" in announcing the end of talks.
The UN Security Council was to hold closed-door talks on Yemen later Monday, diplomats said.
Hadi tendered his resignation on Thursday along with Prime Minister Khalid Bahah, saying he could not stay in office as the country was in "total deadlock".
The crisis had escalated on January 17 when the Huthis seized Hadi's chief of staff, Ahmed Awad bin Mubarak, in an apparent bid to extract changes to a draft constitution.
Pitched battles then erupted in the capital, with the Huthis seizing the presidential palace and firing on Hadi's residence in what authorities said was a coup attempt.
The unrest has raised fears of strategically important Yemen, which lies next to oil-rich Saudi Arabia and along key shipping routes, collapsing into a failed state.
Yemeni authorities have long allowed the United States to carry out drone attacks against Al-Qaeda in the Arabian Peninsula (AQAP), considered by Washington as the jihadist network's most dangerous branch.
US President Barack Obama on Sunday vowed to keep pursuing AQAP despite the crisis, saying "we will continue to maintain the pressure that is required to keep the American people safe".