Back-to-back suicide bombings in Israel and the West Bank have left at least two Israelis dead and 12 others injured. The bombings have shattered a period of relative calm that has prevailed since Palestinian militants declared a three-month ceasefire at the end of June.

Less than an hour after an explosion at a shopping center in the central Israeli town of Rosh Ha'Ayin killed one Israeli, a second blast left another Israeli man dead near the entrance to the nearby West Bank Jewish settlement of Ariel.

Several of the injured are reported in serious condition.

The blast at the shopping center started a fire that burned down several stores.

Security officials put the area on high alert shortly before initial reports about the explosions were received. They said they had received 21 warnings Tuesday morning of possible terrorist attacks.

Spokesmen for Hamas and Islamic Jihad said they did not know who was behind the attacks, and they said both groups remain committed to the ceasefire.

Palestinian Prime Minister Mahmoud Abbas cut short a visit to Gulf Arab states in response to the bombings. The Palestinian Authority condemned the attacks, but Palestinian cabinet minister Yasser Abed Rabbo accused Israeli Prime Minister Ariel Sharon of what he termed all forms of provocations.

A spokesman in Mr. Sharon's office said the attacks showed the need for the Palestinian Authority to take immediate steps to dismantle what he termed the terror infrastructure.

In response to the terror attacks Israel decided to delay the release of dozens of Palestinian prisoners originally set to be freed Tuesday afternoon. The men had been serving criminal sentences and were not connected to militant activity.

Tuesday's attacks follow a period of relative calm that came after the main Palestinian militant groups declared a temporary ceasefire that was to run through September.

On July 7, one woman was killed in a suicide bombing that destroyed her home in the town of Yabetz, north of Tel Aviv.