An unknown gunman has killed environment minister Emmanuel Niyonkuru in the conflict-ridden East African nation of Burundi, a police spokesman said Sunday, according to dpa. The minister was shot dead with a pistol in the early hours of Sunday in the streets of the Rohero neighbourhood in the capital, Bujumbura, police spokesman Pierre Nkurikiye said on Twitter. Police arrested a woman over her alleged involvement in the assassination, the spokesman added.