HONG KONG (AP) — Hong Kong authorities arrested eight people Monday in connection with an unauthorized protest at a university campus last month, amid a widening crackdown on dissent in the semi-autonomous Chinese territory.

The arrests were made in relation to a demonstration at the Chinese University of Hong Kong in which more than 100 people protested a decision to hold graduation ceremonies online. Such ceremonies are often used as a way for students to express political views.

Some protesters had called for Hong Kong's independence, and held up signs that read “Liberate Hong Kong, Revolution of our times,” which are considered to have secessionist notions and are outlawed under the city’s national security law.

Police said they arrested eight people for an unauthorized protest and inciting secession, but did not specify who they were.

"We only arrested those who were shouting slogans, displaying flags that involved some national security concerns,” Li Kwai-wah, senior superintendent of police of Hong Kong's National Security Department, said at a news conference.

Arthur Yeung, a graduate from the university who also ran in the city’s district council elections last year, is suspected to be among those arrested. A post on Yeung’s Facebook page said he was arrested at his home on Monday morning.

Two district councillors, Isaac Lee and Eason Chan, were also arrested, according to posts on their respective Facebook pages.

The eight arrested are currently being investigated by national security officers, according to local newspaper South China Morning Post, which cited unnamed sources.

The arrests come as Hong Kong and Beijing have increasingly clamped down on dissent in the city, following Beijing’s imposition of a national security law in Hong Kong in June aimed at curbing months of political unrest and anti-government protests last year.

The crackdown has prompted accusations that Beijing is violating the autonomy it promised when the former British colony was returned to China in 1997. It also has triggered warnings that the ruling Communist Party is damaging Hong Kong’s appeal as a global business center and one of Asia’s most dynamic cities.

In response, the U.S. has imposed sanctions on more than 10 Hong Kong and mainland Chinese officials, including Hong Kong leader Carrie Lam.

Asked about a report that the U.S. might sanction more officials, a Chinese government spokesperson in Beijing said that China would respond to any U.S. action with countermeasures.

“We have made it clear many times that China has always resolutely opposed and strongly condemned U.S. interference in China’s internal affairs and the so-called sanctions against Chinese personnel on the basis of the Hong Kong issue,” foreign ministry spokesperson Hua Chunying said.