Prime Minister Ariel Sharon on Thursday urged Israelis not to be afraid to go to the polls to vote in the primary race between Foreign Minister Benjamin Netanyahu and himself after the day's terrorist attacks.

"Israel is standing now in the face of a murderous terrorist attack aimed at murdering and killing Jews," Sharon said during a press conference in Israel. "It's forbidden by us to let the terrorists dictate our lives."

Netanyahu was meeting with foreign ministers and could not attend the news conference.

Gunmen on Thursday opened fire at a Likud Party office crowded with voters and at passengers in a nearby bus terminal in the northern Israeli town of Beit Shean, not far from the Jordanian border.

"The Arab target today is to influence the Israeli election process and the democratic processes in Israel," Sharon said. "The terrorism will not change the way we do business in Israel."

"It's not important who you're supporting, don't let terrorism scare you" during the elections, he said. "Don't let terrorism influence you - go and vote, go and vote."

President Bush, who learned of the attacks during his Thanksgiving intelligence briefing, called them acts of terrorists. He said the United States "remains firmly committed...to fight against terror and those who commit these heinous acts."

"I want to extend my condolences to the victims and their families, and to the governments and peoples of Israel and Kenya," Bush said in a written statement from his Texas ranch, where he was spending Thanksgiving with his family.

"Today's attacks underscore the continuing willingness of those opposed to peace to commit horrible crimes. Those who seek peace must do everything in their power to dismantle the infrastructure of terror that makes such actions possible," Bush said.

Asked whether Al Qaeda is behind Thursday's violence, a White House spokesman said, "it is premature to rule it in or out."

Sharon said his government has taken "additional steps to protect the Israeli people" as they go to the polls, including the use of military personnel to accompany voters to polling places.

Initial voter turnout had been relatively low, which could hurt Sharon's chances. He had about a 20 percent lead over Netanyahu three hours before polls were to close.

Whoever wins the primary is likely to become the next prime minister of Israel, since the results weigh so heavily in the general election, slated for Jan. 28.

Earlier Thursday, Israeli tourists in Kenya were the targets of simultaneous terrorist attacks. A homicide bombing killed 15 and wounded 80. And at least two missiles were fired at, but missed, an Israeli airplane.

Offering his condolences to families of the dead and injured, Sharon urged Israelis to not be frightened by "terrorists or anyone they send against us" and to not let the violence alter the way they live their lives.

Asked by a reporter whether Sharon's camp is still trying to oust Palestinian leader Yasser Arafat, Sharon said: "Israel is waging a campaign against terror and military organizations have own way of doing things … there are many successes, unfortunately, we don't always succeed."

Sharon said at least 15 terrorist attacks have already been thwarted.

"We will continue to act in the same ways, in the right ways, in order to limit terrorism or eliminate it," he said.

Fox News' James Rosen contributed to this report.