LAGOS, June 16 (Xinhua) -- At least four gunmen suspected to be bandits were killed in a shootout with Nigerian police in the north state of Kaduna, police said on Thursday.

       Mohammed Jalige, the police spokesperson in Kaduna, said in a statement a police special tactical engaged on Wednesday the gunmen who were "delivering some dangerous weapons to their cohorts" along an expressway in the Lere local government area of the state.

       "The encounter lasted for about 30 minutes as the firepower of the police forced them to retreat into the forest," Jalige said.

       He said the police operatives injured in the exchange of fire four of the gunmen, who were pronounced dead after being sent to a local hospital in Kaduna.

       A woman suspected of supplying arms and ammunition to bandits within the state was also arrested on Wednesday, according to the police spokesperson.

       There have been a series of gunmen attacks in the most populous African country in recent months, leading to deaths and kidnappings.