An Afghan insurgent group led by the son of late anti-Taliban commander Ahmad Shah Massoud claimed Saturday to have seized three northern districts from the hardline Islamists, after announcing a wide military offensive. The National Resistance Front (NRF), led by Ahmad Massoud, said the action in the Panjshir Valley was its first armed offensive against Taliban forces since they stormed back to power. NRF forces were the last to hold out against the Taliban takeover of Afghanistan in August last year, retreating to the valley which fell in September, weeks after US-backed government troops ca…