HONG KONG — After firing multiple rounds of tear gas, riot police officers on Saturday briefly clashed with protesters inside the same Hong Kong train station where an armed mob had attacked demonstrators last weekend.

Tens of thousands of protesters had converged on the northern district of Yuen Long to show their opposition to an assault by more than 100 men, armed with sticks and metal bars, on demonstrators and others there last Sunday night that had left at least 45 people injured.

What started out as a peaceful rally descended into brief clashes and chaos at the train station where last week’s attack had taken place. After getting the protesters off the streets with round after round of tear gas, the riot police stormed the train station where protesters had retreated, and brief clashes ensued before the officers backed away.