March 23, 2011  -- The bomb that exploded today in Jerusalem, Israel, killing one and injuring more than 20 others, may have been trigged by remote control to go off just as a bus drove by, officials told ABC News.

The bomb, which was packed with more than a kilogram of explosives and shrapnel, was left on the sidewalk near the city's central bus station. One woman who was critically injured in the blast later died, according to several reports.

Jerusalem's mayor, Nir Barkat, told the Jerusalem Post the blast was a "cowardly terrorist attack." An Israeli security official told the Post it was the first terrorist attack using an explosive in Jerusalem in four years.

Television footage from the scene of the incident showed several emergency vehicles surrounding the bus, which had a gaping hole in its side apparently caused by the blast.

"I saw kids crying on the street, lying in blood on the side of the road," one witness told the AP.

No group has claimed responsibility for the attack, but Israeli police suspect Palestinian militants, officials told ABC News. Investigators said the bomb was likely detonated by remote control, or possibly a timer, and is not believed to be part of a suicide bombing.

Israel's interior minister, Eli Yishai, told a local news station Israel should retaliate against "terror organizations" for the attack, which he saw as an escalation of violence. Yishai had reportedly recently returned from a visit to the U.S. and traveled to the scene of the bombing.

"With these murderers, these terrorist organizations... we must act, or we lose our deterrence," he said.

Yishai did not say exactly what actions he was calling for Israel to take, explaining, "I think it would be better not to say what to do or not do."

U.S. Secretary of State Hillary Clinton echoed the need for response.

"Terrorism and the targeting of civilians are never justified," she told reporters today. "Israel, like all nations, of course, has to respond when this occurs. The United States is committed to Israel's security, and we strongly condemn this violence and extend our deepest sympathies to all those affected."

Palestinian Leaders Condemn 'Terrorist Operation', Israel to Assess Security

Hours after the bombing, Palestinian president Mahmoud Abbas and prime minister Salam Fayad condemned the attack.

"I condemn this terrorist operation, in the strongest terms, regardless of which party standing behind it," Fayad said according to the Palestinian News and Information Agency.

The bombing comes on the same day the Israeli Defense Forces announced its planes had bombed a rocket launcher in the northern Gaza Strip that military officials said had been used to fire on an Israeli city in past days. The IDF said a "terrorist cell" of Hamas was operating the rocket launcher.

"The IDF will continue to respond firmly to the firing of rockets and any other type of terrorist activity emanating from the Gaza Strip and will not tolerate any attempts to harm Israeli citizens or IDF soldiers," the IDF said in a statement prior to the Jerusalem bombing. "The IDF suggests that Hamas not attempt to escalate the situation or test the IDF's strength."

U.S. Defense Secretary Robert Gates told reporters today it's "obviously a horrific terrorist attack," but said it did not necessarily signal a deterioration of stability in the region.

In her statement to reporters, Clinton said the U.S. condemned the rocket attacks in addition to today's bombing. Following the bombing, the IDF said Israeli Minister of Defense Ehud Barak would assess Israel's security situation. "We will not tolerate attacks on Israel's civilians, not in communities in the South and not in Jerusalem," Barak said.

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