At least one member of the Izz ad-Din al-Qassam Brigades, Hamas’s military wing, appeared at a public event in the Fatah-controlled West Bank on Sunday.

The man, who was armed and wearing a mask, a military vest and a green bandanna, was photographed at a memorial service for a slain member of Islamic Jihad in the Jenin refugee camp, according to Israel Radio.

He was standing on a makeshift stage flanked by members of Islamic Jihad and Fatah’s military wing, the al-Aqsa Martyrs’ Brigade. Two other Hamas members allegedly filmed the incident.

A source in the Palestinian Authority said that security forces would act to arrest any members of Hamas’s military wing if they received specific intelligence of their presence, as it is forbidden for them to appear in public in the West Bank. However, he qualified that it is difficult to crack down at sensitive events, such as a memorial.

In recent months, there have been several recorded instances of masked gunmen appearing at refugee camps in the West Bank, but until this incident, they had always been members of the ruling Fatah party.

Hamas and Fatah have been continuously at odds since Hamas violently seized control of the Gaza strip in 2007. Palestinian Authority security forces regularly arrest members of Hamas in the West Bank.