The Islamic militant group Hamas claimed responsibility for one of the suicide bombings, marking its first open violation of a unilateral truce it declared June 29.
It was not immediately clear whether this meant the cease-fire was over. Hamas political leaders in the Gaza Strip could not be reached for comment.
Israeli Prime Minister Ariel Sharon said he would not move forward with an already troubled U.S.-backed peace plan "if terrorism doesn't cease completely."
The bombing at the entrance to the West Bank settlement of Ariel killed the assailant and an 18-year-old Israeli army recruit. Less than an hour earlier, another bomber blew himself up outside a supermarket in Rosh Haayin, a town in central Israel. The attacker and an Israeli were killed.
The claim of responsibility was issued on the Web site of Izzedine al Qassam, the Hamas military wing. The bomber was identified as Islam Yousef Qafisha, 21, from the West Bank city of Nablus. The military wing said it carried out the attack in response to what it alleged were Israeli truce violations.
"I saw fire and a cloud of smoke. They brought out an injured child and then his mother," said Avigail Josef, who sells lottery tickets in a booth just feet from the supermarket in Rosh Haayin.
A short time later, an attacker blew himself up at a bus stop near the entrance to Ariel, killing an Israeli and seriously injuring two others. Rescue services identified the dead and injured as teenagers.
"I saw the terrorist on the ground and another young man or girl killed and two others wounded," said the mayor of Ariel, who arrived shortly after the bombing.
Israel accused Palestinian Prime Minister Mahmoud Abbas of not doing enough to prevent attacks. Under a U.S.-backed peace plan, the Palestinians must dismantle militant groups, but Abbas, also known as Abu Mazen, has said he will not confront Hamas, Islamic Jihad and Fatah's Al Aqsa Martyrs' Brigade. Abbas is currently touring Gulf states.
"The fact that Abu Mazen is circling the globe does not show a serious commitment to dealing with terrorism," said Israeli Cabinet minister Gideon Ezra.
In a first response, Israel called off the release of 76 Palestinians from Israeli jails. The detainees, none of them accused of anti-Israeli violence, had already boarded buses Tuesday morning when the convoys were ordered back.
However, it appeared unlikely Sharon would order a large-scale response. He did not change his itinerary Tuesday or convene his security Cabinet, as is customary after major attacks.
The Palestinian leadership condemned the bombings, but said the Israeli accusations were unfair. The Palestinian security chief, Mohammed Dahlan, said he will not permit truce violations and that suicide bombings harm the Palestinian interest.
In Rosh Haayin, a bedroom community not far from Tel Aviv, the bomber struck at the entrance to a supermarket and pharmacy in a small shopping center, leaving a mass of twisted blinds and shattered glass.
"We heard an explosion and I ran downstairs and saw smoke," a witness identified as Roni told Israel's Channel 2 television. "I saw the bomber ... only the upper part of him was intact, he was missing legs and arms. I saw a leg lying nearby," he said.
Two bodies were found at the scene, one belonging to an Israeli and the other the bomber. Nine people were injured, one seriously, five moderately and three lightly.
The blast sparked a large fire in the supermarket in Rosh Haayin. Firefighters with breathing equipment pulled casualties out of the shattered store.
This town is very close to the "green line" between Israel and the West Bank, reports CBS News Correspondent Allen Pizzey, so it's relatively easy for suicide bombers to cross.
In Ariel, the body of the dead Israeli lay spread-eagled at the side of the road, covered by a white plastic sheet. Police and soldiers with sniffer dogs searched for more explosives.
Regional police chief Uri Bar Lev said police had been on high alert after warnings of an attack in the area. Israel TV's Channel 10, citing a Palestinian security source, said Palestinian officials had warned Israel about the Rosh Haayin and Ariel attacks.
"We can't be expected on the one hand to continue to make concessions and on the other hand to receive more suicide bombings," said Israeli Foreign Ministry spokesman Jonathan Peled.
"We will continue to take every measure necessary to protect our civilians as long as the Palestinian Authority doesn't begin seriously fighting against the terrorist infrastructure," he added.
Palestinian legislator Saeb Erekat said the Palestinian leadership "absolutely rejects the Israeli accusation of the Palestinian Authority."
An Israeli security official said that since the June 29 cease-fire, the military had thwarted 36 Palestinian attacks and arrested more than 200 Palestinians.
Tuesday's were the first suicide bombings since a Palestinian from a splinter cell within the Islamic Jihad group blew himself up inside a house on July 7, killing a 65-year-old woman.