At least 42 people have been killed and 20 wounded after gunmen opened fire on vehicles carrying Shia Muslims in Pakistan’s restive north-west, in one of the region’s deadliest such attacks in recent years, police said. The attack happened in Kurram, a district in Khyber Pakhtunkhwa province where sectarian clashes between majority Sunni Muslims and minority Shias have killed dozens of people in recent months. No one immediately claimed responsibility for the latest attack, whose victims included six women. It came a week after authorities reopened a key highway in the region that had been closed for weeks after deadly clashes. Local police official Azmat Ali said several vehicles were travelling in a convoy from the city of Parachinar to Peshawar, the capital of Khyber Pakhtunkhwa, when the attack began. He said at least 10 passengers were in critical condition at a hospital. Aftab Alam, a provincial minister, said officers were investigating to determine who was behind the attack. The interior minister, Mohsin Naqvi, called the shootings a “terrorist attack”. The prime minister, Shehbaz Sharif, and president, Asif Ali Zardari, condemned the attack, and Sharif said those behind the killing of innocent civilians will not go unpunished. Kurram resident Mir Hussain, 35, said he saw four gunmen emerge from a vehicle and start shooting at buses and cars. “I think other people were also firing at the convoy of vehicles from nearby open farm field,” he said. “The firing continued for about 40 minutes.” He said he hid until the attackers fled. “I heard cries of women, and people were shouting for the help,” he said. Ibne Ali Bangash, a relative of one of the victims, described the convoy attack as the saddest day in Kurram’s history. “More than 40 people from our community have been martyred,” he said. “It’s a shameful matter for the government.” Baqir Haideri, a local Shia leader, denounced the assault and said the death toll was likely to rise. He accused local authorities of not providing adequate security for the convoy of more than 100 vehicles despite fears of possible attacks by militants who had recently threatened to target Shias in Kurram. Shop owners in Parachinar announced a strike on Friday in a protest about the attack. Shia Muslims make up about 15% of the 240 million population of Sunni-majority Pakistan, which has a history of sectarian animosity between the communities. Although the two groups generally live together peacefully, tensions have existed for decades in some areas, especially in parts of Kurram, where Shias are the majority. Dozens of people from both sides have been killed since July when a land dispute erupted in Kurram that later turned into widespread sectarian violence. Pakistan is tackling violence in the north-west and south-west, where militants and separatists often target police, troops and civilians. Violence in the north-west has been blamed on the Pakistani Taliban, a militant group that is separate from Afghanistan’s Taliban but linked to them. Violence in south-western Balochistan province has been blamed on members of the outlawed Baloch Liberation Army.