JERUSALEM — Israel will strike at more Hamas leaders, the Israeli defense minister said Tuesday, a day after the founder of the Islamic militant group, Sheik Ahmed Yassin, was assassinated in a missile attack.

Defense Minister Shaul Mofaz and his security chiefs decided to try to kill the entire Hamas leadership, without waiting for another terror attack, security sources said Tuesday.

The killing of Yassin threatens to escalate Israel-Palestinian fighting. Fearing revenge, Israel beefed up security throughout the country and at missions abroad.

Hundreds of thousands of Palestinians thronged the streets of Gaza City for Yassin's funeral procession Monday, and Hamas threatened punishing revenge attacks against Israel. It also hinted that the United States could become a target for backing Israel.

Hamas, founded by Yassin in 1987, wants to destroy Israel and replace it with an Islamic state. Defense Minister Shaul Mofaz said Monday that Hamas killed 377 Israelis and wounded more than 2,000 in hundreds of attacks.

Mofaz said Tuesday that other Hamas leaders would be targeted. "If we will continue, in a determined way, with our strikes against Hamas and other terror groups, with the means I outlined, including action against those leaders, we will bring more security to Israeli citizens," he said.

Mofaz and Israeli security chiefs met for five hours late Monday and decided to step up targeted attacks, the security sources said, speaking on condition of anonymity. They said officials decided to go after the entire Hamas leadership without waiting for another attack by the militant group.

A decision on targeting top Hamas officials was first made last week by Israel's Cabinet, in response to a double suicide bombing at an Israeli seaport.

On Tuesday, Israel's army chief suggested that Palestinian leader Yasser Arafat and the chief of the Lebanese guerrilla group Hezbollah, Hassan Nasrallah, would eventually be assassinated by Israel.

"I think that their responses yesterday show that they understand that it is nearing them," Lt. Gen. Moshe Yaalon said when asked if the two men were in Israel's crosshairs.

Arafat's aides say the Palestinian leader is concerned about being targeted. It was not clear what response by Nasrallah the army chief was referring to.

In Gaza City, thousands of mourners gathered in a reception area set up in a large soccer stadium adorned with green Hamas flags and posters of Yassin. Loudspeakers broadcast calls for jihad, or holy war.

Palestinian Prime Minister Ahmed Qureia headed to Gaza on Tuesday to express condolences and was to attend a ceremony at the stadium later in the day.