Police have arrested a woman in connection to the assassination of a government minister, authorities said. Burundi has witnessed a period of political violence that has left 500 people dead and 300,000 others displaced.

Minutes after midnight local time, a gunman shot and killed Burundi’s Environment Minister Emmanuel Niyokuru, police said in a statement on Sunday.

“Minister of water and environment killed by a criminal with a gun on his way home to Rohero, around 00:45,” said police spokesman Pierre Nkurikiye in a tweet.

Nkurikiye added that authorities arrested a woman linked to the “assassination.”

The East African nation has witnessed a spate of political violence since Burundian President Pierre Nkurunziza announced he would seek a third term despite a constitutional two-term limit.

Nkurunziza effectively won a third term in office in 2015, escalating tensions across the nation. The international community criticized the elections, citing widespread irregularities.

At least 500 people have been killed and 300,000 people displaced due to political violence, the majority of deaths caused by police and armed opposition groups.

The president took to Twitter to offer his condolences “to the family and all Burundians” for the assassination of the environment minister, vowing that the assailant will be brought to justice.

Niyokuru’s assassination marks the first high-profile assassination of a government minister since the president won a third term.

In November, Burundian presidential adviser Willy Nyamitwe survived an attempt on his life. However, he was injured during the attack.