Officials warned on Tuesday of a humanitarian crisis in Helmand as fierce fighting sent refugees fleeing to the capital of the southern Afghan province, with Taliban insurgents tightening their grip despite intensified US air strikes. Helmand, long a hub of militancy and opium production, has seen a recent increase in militant attacks, with fighters seizing more territory in the volatile province since NATO troops withdrew in 2014. The provincial governor's spokesman Omar Zawak said Lashkar Gah is struggling to cope with an influx of people fleeing the fighting elsewhere in the province. "Around 30,000 people have been displaced in Helmand in the past several weeks. Most of them are coming to Lashkar Gah," he said. "It difficult for the city to contain all of them. Families, children, women, all have to sleep on the streets. There is a shortage of food and clean water, we need urgent support." "The shelling is pretty heavy this morning," an official with aid organization Medecins Sans Frontieres in the city said on condition of anonymity. Residents voiced fears the city could fall, saying insurgents had heavily mined the roads and exhausted soldiers were running out of food. "The Taliban are in control of all the roads leading to Lashkar Gah," resident Haji Qayum said. "The police check posts are falling one by one. There is a great fear the capital may fall to Taliban soon too." As the fierce battles continue, NATO has stepped up air strikes supporting Afghan forces on the ground, highlighting the intensity of the combat in Helmand. "The situation down there remains tense and somewhat contested," a NATO spokesman said. "It remains an ongoing security concern and there has been fighting down there for the last several weeks. We remain confident that the Afghan forces are fighting effectively and that they will continue to secure Lashkar Gah." Toryalai Hemat, the provincial governor's media adviser, said NATO's air strikes have inflicted heavy casualties on the Taliban. NATO officially ended its combat mission in December 2014, but US forces were granted greater powers in June to strike at the insurgents as President Barack Obama vowed a more aggressive campaign. The US has deployed several hundred troops in Helmand in recent weeks. Last August Taliban insurgents briefly captured the town of Musa Qala in Helmand before Afghan forces backed by NATO retook it.