A bomb hit a passenger train in Pakistan's restive southwest on Monday, killing at least six people and wounding more than 17 others, officials said. The device, apparently planted on the railway track, exploded when the train approached a station in Naseerabad district, around 250 kilometres (150 miles) southeast of Quetta, the capital of insurgency-hit Baluchistan province. "It was a bomb blast, the target was the passenger train. At least six people have been killed," provincial home secretary Asad Gilani told AFP, adding that more than 17 others were wounded in the blast. Zafar Shah Bukhari, a senior official in the area, confirmed the attack on the Jaffar Express, travelling from Rawalpindi to Quetta, and the death toll. "We have taken the dead bodies and injured to the nearby hospital," Bukhari said, adding that the condition of six of the injured was critical. The explosion derailed the train, Bukhari added. The identity of those killed in the attack was not yet clear but Gilani said some security personnel were travelling in the train. "All those killed were men but women and children were among the wounded," Bukhari said. Police and other security personnel cordoned off the area after the blast. An intelligence official told AFP bomb disposal experts were examining the site to determine the nature of the blast and check for any more devices. Bukhari said one of the compartments of the passenger train was badly damaged due to the intensity of the explosion. Faiz Bugti, a senior railway official in the area, told AFP that the train service had been suspended as the blast has damaged the railway track. Javed Ahmad, another railway official, told AFP that work to clear the track would take hours. No group has yet claimed responsibility for the blast but in the past, the separatist Baluch Republican Army has claimed such attacks. Railways minister Saad Rafique accused Baluch separatists for the attack and told reporters the bomb was detonated by remote-control. "People who claimed to be fighting for the rights of Baluchistan are responsible for this attack," Rafique said. Baluch rebels have been fighting since 2004 for political autonomy and a greater share of profits from the region's natural oil, gas and mineral resources. Impoverished Baluchistan is also a flashpoint for surging sectarian violence between Pakistan's majority Sunni Muslims and Shiites, who account for around a fifth of the country's 180 million people. Pakistan is battling a homegrown Islamist insurgency and faces near-daily bombings and shootings in the troubled northwest, but attacks on the railway are relatively rare. Gunmen in a car shot dead four policemen at a checkpoint in a restive northwestern Pakistani city on late Sunday, officials said. The shooting took place in Peshawar, capital of Khyber Pakhtunkhwa province, where Taliban militants are active.