The growing violence underscores rising insecurity in Afghanistan over the resurgent Taliban.
The country is bracing for an intense fighting season in the spring as the government's repeated bids to launch peace negotiations with the Taliban have failed.
Afghan forces, already beset by record casualties, desertions and non-existent "ghost soldiers" on the payrolls, have been struggling to rein in the Taliban since US-led NATO troops ended their combat mission in December 2014.