GAZA CITY  - The United Nations condemned the firing of a rocket from Gaza into Israel which it said had broken the longest ceasefire between the two sides in recent years. Fighters from Fatah’s Al-Aqsa Martyrs Brigades fired the rocket in a response to the death of a Palestinian prisoner in an Israeli jail at the weekend. There are mounting international fears that serious new unrest could erupt in the Palestinian territories. “This was the longest period without projectiles fired from Gaza in recent years, and both sides should work to consolidate the calm that prevailed before today,” UN political chief Jeffrey Feltman told a UN Security Council meeting on the Middle East. He said the UN was “deeply troubled” by the rocket attack, which was the first since an Egyptian-brokered ceasefire ended a showdown between Gaza and Israeli forces in November. Just three weeks before a top-level visit by US President Barack Obama, his first since becoming president, Israel has been grappling with fears that the rising anger over the prisoners could spark a third intifada, or uprising. But following four consecutive days of clashes between protesters and troops, the demonstrations appeared to be tailing off on Tuesday, with Palestinian police in the northern West Bank moving to prevent protesters from gathering at Jalame checkpoint, an AFP correspondent said. Tuesday’s rocket marked the first time fighters had fired across the border in more than three months following an Egyptian-brokered truce deal which ended eight days of deadly fighting in November.