The European Union on Monday called on all sides in Hong Kong to exercise restraint and said that any violence is "unacceptable".
Maja Kocijancic, a spokeswoman for the EU Commission, said in a news briefing in Brussels that the EU continues to monitor the situation in Hong Kong.
"We repeat our call to all sides to exercise restraint and engage constructively in efforts to deescalate the situation," she stressed.
"Any violence is unacceptable," Kocijancic added.
She said actions by the law enforcement authorities must remain strictly proportionate.
Kocijancic said fundamental freedoms, including the right of peaceful assembly and expression, must be upheld.
More than 50 protesters were detained on Monday as Hong Kong police lay siege to a university.
The Hong Kong Polytechnic University occupied by protesters since last week has become a hotspot of clashes in more than five months of political unrest.
Hong Kong, an autonomous region under China since 1998, is witnessing protests since early June, against the Carrie Lam administration’s move to legalize extradition to mainland China.
The government has already dumped the bill, but protests continue with demands to prosecute the police for violence.
In a related development Monday, the High Court ruled that a mask ban imposed by the government was incompatible with Basic Law, the city's mini Constitution.
The Lam administration imposed a harsh mask ban on Oct. 5 after protesters hid their identity. Many people were charged and detained for defying the ban.