A sergeant and three constables were injured when they were attacked by a man yesterday during a raid on a gambling den allegedly controlled by triads in Tsuen Wan. The officers raided a flat in Chuen Lung Street and arrested 12 men and two women at 1.30am. Police said 12 of them were playing mahjong. Police seized chips, $39,000 in table money and gambling paraphernalia. A police spokeswoman said one of the 12 men assaulted the officers when he was grabbed outside the flat. The 29-year-old, who was unarmed, was eventually overpowered. The four injured police were treated at Yan Chai Hospital. All 14 suspects were held for questioning at Tsuen Wan police station. The assault is the latest of a series of incidents in which police have been taunted and abused by gangsters. On Sunday, three officers were assaulted when they tried to disperse a group of drunken men in Tsim Sha Tsui. Police reinforcements arrived and arrested two alleged members of the Sun Yee On triad society. It is understood another member of the group hurled abuse at an officer but was not arrested. There were two other incidents in Yau Ma Tei and Tsim Sha Tsui East over the weekend in which officers were abused by suspected gangsters. One officer was also injured in the Yau Ma Tei incident.