Hong Kong riot police stormed several shopping malls where pro-democracy demonstrators had gathered amid the peak shopping weekend before Christmas.

Protesters wearing all black were staging sit-ins and singing in the malls as they continued calls for reform and investigation of police tactics used against them since the demonstrations began in May.

In a mall in Yuen Long near the Chinese border, demonstrators marked the five-month anniversary of an attack in a train station by an armed mob wearing white T-shirts that beat up bystanders and protesters with pipes and poles, Reuters reported.

“Yuen Long is no longer a safe place … and we all live in white terror when we worry if we will be beaten up when dressed in black,” said a 30-year-old clerk whose last name is Law.

Hong Kong police were criticized for a slow response to calls for help, and for not arresting anyone in the mob at the scene. They later made six arrests and said the attackers were part of an organized criminal gang. They haven’t been prosecuted yet.

In the upscale Harbour City mall Saturday, dozens of riot police suddenly ran into the mall, a luxurious shopping center, after plainclothes officers tackled a few demonstrators, journalist Phoebe Kong reported. The plainclothes officers were dressed in black like the protesters.

“We can’t celebrate Christmas when our city is taken over by the police. When you see the police outside the mall, do you feel like shopping for presents?” said Bob, 17, a protester.

Separately, about 3,800 people attended a rally held outside detention centers demanding the release of arrested protesters, Kong reported.

The demonstrations are aimed at stopping what Hong Kong residents see as China’s meddling in the city’s freedoms guaranteed under the “one country, two systems” formula.

Many are also outraged by perceived police brutality, and are demanding an independent investigation into allegations of excessive force. Hong Kong police have promised to take a more “flexible” approach to the protests.