The Hamas Islamic militant organisation, which condemned the deal, has made a number of attacks over the past month that culminated in the killing of two Israeli hikers near Megiddo last weekend.
Last night's explosions, in Haifa and Tiberias, will put pressure on Ehud Barak, the Israeli Prime Minister, not to go ahead with the release of 350 Palestinian security prisoners over the next six weeks.
Hamas has been badly damaged by the Israeli and Palestinian security services since 1996, when suicide bombs killed 60 Israelis and ensured the poll victory of Benjamin Netanyahu. Israeli and Palestinian security said Hamas planned attacks, and claimed to have prevented a number of attempts. Last night, the Israelis were not confirming that the explosions were car bombs but they came so close together in cities only 50 miles apart that co-ordination is likely.
The two dead in Tiberias and the one in Haifa were said have been occupants of the cars. If they were premature explosions, this is in keeping with the last suicide attack, in which two men in a car blew themselves up. Hamas may no longer be able to mount the sophisticated attacks it carried out in 1995 and 1996.
Nevertheless, suicide attacks in Israel have a proven ability to change the political mood. Mr Netanyahu won the 1996 election by saying peace deals with the Palestinians had reduced, not increased, Israeli security. If Hamas was behind the bombs there may have been another motive. Last week Jordan, under pressure from Israel, the United States and Yasser Arafat, the Palestinian leader, closed the Hamas offices in Amman. They had remained open even during previous suicide attacks. Hamas may have wanted to show it still has the capacity to make attacks.
Earlier, Mr Barak told his cabinet the main Israeli achievement in renegotiating the Wye agreement was to put off transferring key territory to Palestinians until talks on a permanent settlement of all remaining issues in dispute got under way.
International applause for the deal signed by Mr Barak and Mr Arafat was in contrast to the more muted reaction of Israelis and Palestinians,waiting to see the effects of the agreement on the ground.
Talks on agreeing a framework of principles for resolving final-status issues - Jerusalem, Palestinian refugees, Jewish settlements, borders, Palestinian statehood and access to water - start on 13 September.
Ariel Sharon, elected leader of the opposition Likud party just as the deal was being agreed, said it was a lie to say Mr Barak had improved on what was previously negotiated. He called on the Prime Minister not "to release prisoners with blood on their hands".
Syria reacted negatively to the Sharm el-Sheikh agreement: the official Tishreen newspaper said the issue was not to sign accords but to see how these responded to the rights and and aspirations of the peoples of the region. "Syria strongly rejects being dragged into the game of signing agreements and deals to implement previously agreed accords," it said.