Three policemen and a civilian were killed after a group of gunmen opened fire on a deputy governor’s convoy in central Nigeria, local police confirmed on Wednesday.

Emmanuel Akabe, deputy governor of the central state of Nasarawa, escaped unhurt, police spokesman Usman Samaila said. The convoy, which came under attack on Tuesday, was taking Akabe and some of his aides to the Nigerian capital, Abuja, the spokesman said.

The gunmen fled the scene after the attack, he said.

An investigation has been launched to apprehend the attackers, Samaila added.