The Palestinian Islamist Jihad said Monday that Hamas-run security forces in the Gaza Strip had briefly detained its fighters to prevent them from attacking Israeli troops.
"Four members of al-Quds Brigades (Islamic Jihad's armed wing) were released after being detained by Hamas-run internal security services in northern Gaza for over four hours," an official said on condition of anonymity.
"The group's weapons and possessions were confiscated and they were forced to sign an oath not to undertake any jihad (holy war) actions against the Zionist enemy because of an unannounced period of calm."
Hamas spokesmen could not immediately be reached for comment.
Both Israel and Hamas declared unilateral ceasefires at the end of the 22-day Gaza war in January 2009, but Palestinian fighters have occasionally fired rockets and Israel has carried out some limited incursions since then.
Hamas has said it and other fighting groups have agreed to suspend rocket fire but have vowed to fight back if Israeli forces cross into Gaza.
But Islamist Jihad, a smaller and more radical Islamist group, has rejected such ceasefires in the past, and on Monday the official said "there is absolutely no period of calm between the resistance and the enemy."
The number of rockets fired from Gaza has dropped by around 90 percent since the end of the war as Hamas has quietly reined in smaller armed groups.