BEIJING (AP) — Chinese universities sent students home and police fanned out in Beijing and Shanghai to prevent more protests Tuesday after crowds angered by severe anti-virus restrictions called for leader Xi Jinping to resign in the biggest show of public dissent in decades.

Authorities have eased some controls after demonstrations in at least eight mainland cities and Hong Kong — but showed no sign of backing off their larger “zero-COVID” strategy that has confined millions of people to their homes for months at a time. Security forces have detained an unknown number of people and stepped up surveillance.

With police out in force, there was no word of protests Tuesday in Beijing, Shanghai or other major mainland cities that saw crowds rally over the weekend. Those widespread demonstrations were unprecedented since the army crushed the 1989 student-led pro-democracy movement cantered on

Beijing’s Tiananmen Square.

A far smaller group did gather at a university in Hong Kong on Tuesday to protest virus restrictions.

Meanwhile, Beijing’s Tsinghua University, where students rallied over the weekend, and other schools in the capital and the southern province of Guangdong said they were protecting students from COVID-19 by sending them home.

But dispersing them to far-flung hometowns also reduces the likelihood of more demonstrations. Chinese leaders are especially wary of universities, which have been hotbeds of activism including the Tiananmen protests.

On Sunday, Tsinghua students were told they could go home early for the semester and that the school would arrange buses to take them to the train station or airport.

Nine student dorms at Tsinghua were closed Monday after some students positive for COVID-19, according to one who noted the closure would make it hard for crowds to gather. The student gave only his surname, Chen, for fear of retribution from authorities.

Beijing Forestry University also said it would arrange for students to return home. It said its faculty and students all tested negative for the virus.

Universities said classes and final exams would be conducted online.

Authorities hope to “defuse the situation” by clearing out campuses, said Dali Yang, an expert on Chinese politics at the University of Chicago.

Depending on how tough a position the government takes, protests could continue on a “rotational” basis, with new groups taking turns, he said.

But many people are nervous after police detained some protesters and warned them against demonstrating again.

In Shanghai, police stopped pedestrians and checked their phones Monday night, according to a witness, possibly looking for apps such as Twitter that are banned in China or images of protests. The witness, who insisted on anonymity for fear of arrest, said he was on his way to a protest but found no crowd there when he arrived.

Images viewed by The Associated Press of photos from a weekend protest showed police shoving the people into their cars. Some people were also swept up in police raids after demonstrations ended.

One such person, who lived near the site of a protest in Shanghai, was detained Sunday and held until Tuesday morning, according to two friends who also insisted on anonymity for fear of retribution from authorities.

In Beijing, police on Monday visited a resident who attended a protest the previous night, according to a friend who refused to be identified for fear of retaliation. He said the police questioned the resident and warned him not to go more protests.