A group of unidentified armed men attacked North Sumatra's Hamparan Perak police station at 0.30 am Wednesday, killing three police personnel. A policeman of the police headquarters said the three police personnel who were shot dead by the attackers were Adjunct Inspector I Baik Sinulingga, Adjunct Inspector I Deto Sutejo and Chief Brigadier Riswandi. He said that the number of attackers were estimated to reach ten persons. They used motorcycles and attacked the police post with firearms. Besides killing three police personnel, the attackers also caused damage to the window glasses of the Hamparan Perak police headquarters due to the bullets, ANTARA reported. North Sumatra Regional Police Spokesman Snr Commissioner Baharudin Djafar said his side was still investigating the case. He said that North Sumatra Police Chief Inspector General Oegroseno had ordered all of his ranks and files to increase vigilance.