BEIJING - A three-day international exhibition of police equipment began in Beijing on Wednesday, demonstrating sophisticated technology and techniques in anti-terrorism, criminal investigation and drug control operations.

A total of 239 companies participated in the biennial exhibition, the fifth of its kind, and a number of police technology products made their debuts, according to the Ministry of Public Security, the event's organizer.

The exhibition aims to provide a platform for police departments at various levels to learn the field's latest developments and promptly upgrade their equipment in order to improve criminal investigation capabilities.

Displayed techniques included domestically-made DNA reagents, underwater metal video detectors and liquid security check systems.

The latest technological development regarding criminal investigation and material evidence appraisal was also introduced, such as blurred-image recovery techniques and physical and chemical inspection techniques.