In a move which could complicate attempts to reconcile with Iran, Gaza's Hamas rulers have banned a Shia Islamist group loyal to the Iranian regime.
Harakat al-Sabireen (The Sabireen Movement) is a relatively small, armed Shia group in Gaza, whose population is overwhelmingly Sunni.
Though not officially designated as a terrorist group by most western states, it is believed to be funded by Tehran and swears allegiance to the founder of the Islamic Revolution, Ayatollah Khomeini.
The group models itself on Hezbollah, using Hezbollah imagery in its flag and literature, and voicing staunch support for Hezbollah and the Syrian regime of Bashar al-Assad – though it denies any formal links to the Lebanese terrorist group.
The ban was announced Monday by media outlets close to Hamas, with the reason given being that the group was trying to "spread Shi'ism" in Gaza.
Its leader, Hisham Salem, is a former member of Islamic Jihad – Hamas's main rivals in Gaza and an Iranian proxy group – and has reportedly been detained indefinitely by Hamas authorities.
The ban is likely to inflame tensions with Shia Iran, which has had a stormy relationship with Sunni Hamas since the outbreak of the Syrian civil war.
Hamas's refusal to back the Assad regime led to a break in ties with Iran, though more recently Iranian support has returned to some extent.
It comes as Hamas faces numerous challenges to its position in Gaza. Apart from its rivals in Islamic Jihad, Hamas is facing a mounting insurgency from Salafi Islamist groups affiliated with ISIS, and is also under pressure from the Sisi government in Egypt, which accuses Hamas of aiding ISIS in the Sinai Peninsula.
Egypt is also wary of Iranian influence in the region, and may have pressured Hamas to act against a group so clearly tied to Tehran and its radical Shia ideology.
But Hamas's leadership is also facing mounting pressure from its rank-and-file Sunni members, who are uncomfortable with the move to reconcile with Shia Iran while Tehran continues to back the Assad regime's bloody crackdown on Sunni rebels in Syria. In particular, the recent visit by a senior Hamas delegation to break the Ramadan fast with senior Iranian and Hezbollah officials triggered an angry outcry by some Hamas members, who took to social media to voice their displeasure.
Banning a relatively small but visible Shia Islamist group would be an easy way for Hamas to prove it isn't "betraying" its Sunni allegiances.