Tanzania Police Killed In Highway Ambush
The police were attacked while driving from patrols back to Bungu village, 110km (70 miles) south of the main city Dar es Salaam, local media report.
Police say they pursued the bandits back to their hideout, killing four of them in a shootout.
President John Magufuli has expressed his shock at the officers' deaths.
Police described the attack as "banditry" and said that the attackers had stolen weapons.
The BBC's Sammy Awami in Dar es Salaam says attacks on police and police stations, where bandits make away with weapons, are relatively common in Tanzania.
Home Affairs Minister Mwigulu Nchemba has announced a wide-ranging investigation into the killings,