At least six people were killed in a blast that struck a passenger minivan in Afghanistan's western Herat province on Saturday. According to local Afghan media Tolo news, Herat commander Mawlawi Ansari said that six people were killed and nine others received injuries in the blast targeting a minivan in Herat city of the province. The cause of the blast was not clear. The head of Herat's provincial hospital, Arif Jalali in a statement to media said, "Four women were among the seven killed." The condition of three injured people is reported critical. According to initial reports, the bomb was attached to the fuel tank of the bus. No group has so far claimed responsibility for the attack. The blast was confirmed by Herat's intelligence office. "Initial reports indicate it was a sticky bomb attached to the fuel tank of the passenger vehicle," said Sabit Harwi, a spokesman for the office. Herat provincial police and the department of culture also confirmed the bomb blast. No group has so far claimed the attack. A health official in Herat, who asked not to be named, said an explosion hit a small van used for public transport just after 1800 local time and that three of the injured were in serious condition. Since the Taliban took over in August, a series of blasts and attacks, some claimed by Daesh (so-called IS), have taken place across Afghanistan. The attacks have heightened the new administration's security challenges as the country spirals into an economic crisis. Daesh has regularly targeted the country's Shiite Hazara community with deadly attacks, and the area where Saturday's blast occurred near a bus station is also inhabited by the community. Herat is the country's third-biggest city, close to the border with Iran, but had remained relatively peaceful in recent months. — Agencies