QUETTA, Sept 25: Three policemen and a terrorist were killed and three others injured on Saturday when unknown attackers ambushed the official vehicle of a DSP investigation in Wahdat Colony.

"It was a sectarian terrorist attack," Pervez Rafi Bhatti, DIG Quetta Range, told Dawn, adding that unknown armed men waiting for police officer Nisar Kazmi had opened indiscriminate fire at his vehicle.

"Kazmi was their target as he was the main police officer playing an important role in the investigation into terrorist attacks in Quetta and close to exposing the main gang," he said.

"A head constable and two other policemen died on the spot while the attacker succumbed to his injuries in a hospital," police officials said, adding that the injured include DSP (CIA) Nisar Kazmi and one of his security guards.

Another policeman identified as Mohammad Ismail was also injured later in the exchange of fire with the armed men in the Khrotabad area, a locality on the outskirts of Quetta, where the injured attacker was found, a senior police officer said.

According to police sources, DSP Nisar Kazmi had left his house in Wahdat Colony at around 9.45am for the CIA centre. When he reached near a small causeway at the intersection of Killi Deba and the colony, unknown armed men sitting in a Suzuki van opened indiscriminate fire on the vehicle, killing three policemen and injuring two others, including Nisar Kazmi.

Police guards returned the fire and injured a terrorist. After the attack, the outlaws escaped towards Khrotabad area in the van.

Soon after the incident, senior police officers and other authorities concerned rushed to the spot, along with heavy contingent of police and other law enforcement agencies, and started investigation. The injured were rushed to the Bolan Medical Complex.

Police mobiles chased the fleeing attackers and found the Suzuki van abandoned in the Kharotabad area and another vehicle snatched from a carpet merchant.

The police continued the chase and after heavy exchange of fire arrested an attacker who was badly injured. He was also rushed to Bolan Medical Complex where he succumbed to the injuries.

"The attacker jumped a wall during the exchange of fire with the law enforcement agencies," a police officer said, adding that a bullet had hit his head.

Police officials believe that another injured attacker was hiding in the Khrotabad area. He was injured when the security guards had returned the fire, they said.

"He will be arrested soon," DIG Pervez Rafi Bhatti said. However, the police has yet to identify the accused assailant died in the hospital.

The condition of DSP Nisar Kazmi and the two police constables was stated to be stable.

The three policemen killed in the attack were identified as head constables Younas Changezi and Mazhar Ali, and driver Khuda Bakhsh.

Meanwhile, shops, markets, shopping centres and business establishments were closed in the provincial capital as a rumour spread in the city that some shops had been attacked.

The whole city was closed down within a few minutes and local buses stopped plying in the area. Immediately, the police and other law enforcement agencies were deployed in the main bazaars to meet any untoward incident.

The police through megaphones asked the business community to open their shops and markets while same announcements were also made from the main mosques of the city.

"We have deployed extra police force in the city to avoid any untoward incident in retaliation to this tragic incident," said a senior police officer.