Hours after a declared truce to end five days of violence with militants in Gaza, Israeli troops launched a raid into the West Bank and rounded up 50 alleged Palestinian activists.
The arrests sparked more clashes with local youths undermining attempts to ease tensions in the region.
Earlier in Gaza City a masked spokesman for the Popular Resistance Committees had agreed to a temporary ceasefire. Hamas has said it will ensure smaller militant groups will observe the truce.
But within a few hours of the ceasefire coming into effect, two rockets fired from Gaza landed harmlessly in southern Israel.
Lieutenant Colonel Avital Leibovich, Israel Defence Forces spokeswoman said “Still today one million Israelis are close to shelters or in shelters because of the rocket fire.”
The recent flare up of violence was triggered by a Palestinian raid on Israel. Subsequent Israeli airstrikes and rocket barrages from Gaza have left 28 people dead.