University College Dublin (UCD) has advised its students on exchange in two universities in Hong Kong to return home.
The students, thought to number fewer than five in total, have been studying in the Chinese University of Hong Kong (CHUK) and the University of Hong Kong (HKU), both of which have closed for the remainder of term.
UCD Registrar Professor Mark Rogers said they had been in touch with the students and the Department of Foreign Affairs.
"We have recommended to our students that they return home, and working with our partner universities, we are providing them with the services and supports they need to do so," said Prof Rogers.
Hong Kong pro-democracy protesters paralysed parts of the city for a fourth successive day on Thursday, forcing schools to close and blocking highways, as students built campus barricades and the government dismissed rumours of a curfew.
Protesters have torched vehicles and buildings, hurled petrol bombs at police stations and trains, dropped debris from bridges on to traffic below and vandalised shopping malls and campuses, raising questions about how and when more than five months of unrest can be brought to an end.
Chinese President Xi Jinping, speaking in Brazil, said stopping violence was the most urgent task right now for Hong Kong, China's state CCTV television reported.
He said China continued to firmly support Hong Kong leader Carrie Lam. China has a garrison of up to 12,000 troops in Hong Kong who have kept to barracks since 1997, but it has vowed to crush any attempts at independence, a demand from a very small minority of protesters.
The unrest was triggered by what many see as the stifling by China of freedoms guaranteed under the "one country, two systems" formula put in place when Hong Kong returned to Chinese rule in 1997.
China denies interfering in Hong Kong and has blamed Western countries, including Britain and the United States, for stirring up trouble.
Anger grew over perceived police brutality as the protests intensified. Police deny being heavy handed and say they have shown restraint in the face of potentially deadly attacks.
Thousands of students hunkered down at several universities on Thursday, surrounded by piles of food, bricks, petrol bombs, catapults and other homemade weapons.
Police said the Chinese University, in the New Territories, had become a "weapons factory and an arsenal" with bows and arrows and catapults.
"Their acts are another step closer to terrorism," Chief Superintendent (Public Relations) Tse Chun-chung told a briefing, referring to protests on campuses across the Chinese-ruled city.
He also said police would temporarily avoid directly clashing with "high-spirited rioters" to give themselves a breather and avoid injuries.
Police said arrows were fired at officers from Hong Kong Polytechnic University in the morning.
Several Hong Kong universities announced there would be no classes on campuses for the rest of the year.
Baptist University, next to a People's Liberation Army base in Kowloon Tong, issued an "urgent appeal", telling students to stay away from campus.
"Your safety is so dear to our hearts and to your parents' and friends' hearts," it said. "Please stay away from harm's way."
China's Global Times tabloid, owned by the official newspaper of the ruling Communist Party, the People's Daily, said on Twitter that the Hong Kong government was expected to announce a weekend curfew after some of the worst violence in decades in the former British colony.
It deleted the post after a short time. The Hong Kong government said the rumours were "totally unfounded".
Hundreds of protesters occupied roads in the city's business district, home to some of the world's most expensive real estate, in the middle of the day.
Across the harbour, black-clad protesters and students maintained their blockade of major roads, including the entrance to the Cross-Harbour Tunnel that links Hong Kong island to the Kowloon area, and a highway between Kowloon and the rural New Territories.
Police fired tear gas near the tunnel early on Thursday to try to clear the protesters. Roads were strewn with bricks in Stonehenge-like formations and other debris, causing widespread traffic jams.
Protesters threw petrol bombs at the Kowloon-side tunnel turnstiles late in the evening and the tunnel remained closed.
At the Polytechnic University, near the same tunnel entrance, hundreds of students wearing gas masks readied for confrontation. They were practising throwing petrol bombs and archery in a half-empty swimming pool.
Boxes of petrol bombs were placed at vantage points overlooking roads, including the tunnel, which has been blocked since Wednesday evening.
Violence has escalated in recent days, with police shooting and wounding one protester at close range and one man described as a "rioter" dousing a man with petrol before setting him on fire.
The man who was shot was in stable condition. The man who was lit on fire suffered burns to his torso and head, and was in critical condition.
There was also a tense standoff between chanting protesters and police in the New Territories town of Sheung Shui.
Police said they would appoint 100 Correctional Services Department staff, who look after prisons, to reinforce the streets.
"I cannot see how adding 100 special police will help much," democratic lawmaker Tanya Chan told Reuters. "I don't know why the government doesn't adopt measures that can soften the tension rather than intensify conflict."
With reporting from Reuters