KABUL — Taliban forces on Friday captured the city of Zaranj, the capital of Afghanistan"s southwestern Nimroz province, on the border with Iran as the first provincial capital to be seized by the group after United States troop"s withdrawal from the country. Local officials said the Taliban had captured Zaranj, in Nimroz province, in a major blow to government forces. According to local media Tolo news, Taliban attacked the provincial capital on Thursday night and captured it on Friday. Taliban are now controlling three districts of Nimroz out of five. Taliban forces has taken over dozens of districts and border crossings in recent months and heavy clashes are under way in Herat in the west and Kandahar in the south. The insurgents continue to make rapid advances across the country as foreign troops withdraw. They have taken swaths of countryside and are now targeting key cities. Other provincial capitals under pressure include Herat in the west, and the southern cities of Kandahar and Lashkargah. The UN"s special envoy for Afghanistan, Deborah Lyons, on Friday said the war there had entered a "new, deadlier, and more destructive phase", with more than 1,000 civilians killed in the past month. She warned that the country was heading for "catastrophe", and called on the UN Security Council to issue an "unambiguous statement that attacks against cities must stop now". Taliban had seized the governor"s office, the police headquarters and an encampment near the Iranian border in Zaranj, said reports. The attacks were followed by hundreds of residents of the city, flocking towards the border with Iran, in a desperate search for safety. Meanwhile, the deputy governor of Jowzjan province, Abdul Qader Malia told the media that at least 10 Afghan soldiers and a commander of armed members belonging to the Abdul Rashid Dostum militia group in Afghanistan"s northern Jowzjan province were killed. Around nine of the 10 districts of Jowzjan were now controlled by the Taliban and the contest to control Sheberghan, the provincial capital, was under way. Moreover, Taliban also closed a key border crossing with Pakistan on Friday, saying no one would be allowed through. Last month, the Taliban captured the southeast Chaman-Spin Boldak border crossing from Afghan forces. Taliban spokesman, Zabihullah Mujahid in a statement to media confirmed that the group"s leadership had endorsed the move, and on Friday the border had been closed Later on Friday, the UK government advised all its citizens in Afghanistan to leave because of the worsening security situation. Pictures posted on social media showed civilians looting items from government buildings. Taliban insurgents were photographed inside the local airport and posing at the entrance to the city. The last time the Taliban captured a provincial capital was in 2016, when they briefly held the northern city of Kunduz. The militants launched a major military campaign in May, to coincide with the phased withdrawal of US and NATO forces after 20 years of military operations. The capture of Zaranj will add to their momentum, analysts say. — Agencies