A group of IDF soldiers on patrol in Hebron clashed with some 250 Palestinians after trying to arrest a Palestinian policeman on Thursday in the West Bank city of Hebron.

One soldier was punched in the face by a Palestinian policeman in the divided city. Over 20 Palestinians were injured in the clashes, according to Palestinian news agency Ma’an.

Maariv reported that the incident started when the soldiers attempted to arrest a Palestinian policeman. Other policemen and civilians jumped into the fray and threw stones at the soldiers.

Finding themselves overwhelmingly outnumbered, the soldiers retreated while throwing stun grenades and tear gas at the crowd. The soldiers also reportedly fired rubber bullets at the crowd.

The incident took place in the Bab al-Zawiye neighborhood west of Hebron’s Old City, according to Ma’an. The neighborhood is in area H1, which is under full Palestinian control, though Israeli soldiers occasionally enter escorted by Palestinian forces.

It was not immediately clear why the soldiers attempted to arrest the policeman. The city, home to the Cave of the Patriarchs, is a frequent flashpoint of settler-Palestinian tension.

An IDF spokesperson said the army sees the incident as very serious and has opened an investigation.