Baghdad: The Islamic State group has been reluctant to use humans to carry bombs because of the group's reduced numbers, so it has tried out a new tactic: bovine suicide bombers.

Residents of al-Islah, Iraq, say they have witnessed "a strange" sight: two cows harnessed to explosive vests roving the northern side of the village, according to Colonel Ghalib al-Atyia, the spokesman for the police commander in Diyala province.

The animals wandered into the outskirts of the community, and when they seemed close to houses, the bombs were detonated remotely, killing the cows, and damaging nearby houses, but not harming any people, Atyia said.

In the colonel's assessment, the attack signalled that the terrorist group, whose ranks were sharply reduced by its four-year fight against Iraqi security forces backed by US special forces, was resorting to unconventional methods since they lacked manpower.