A woman was killed and more than 30 people injured, three of them seriously, when a bomb exploded yesterday at a crowded Jerusalem bus stop. A gag order has been imposed on the investigation.

The blast took place at about 3 P.M. outside Jerusalem's International Convention Center (Binyanei Ha'uma ), just opposite the central bus station. The casualties were evacuated to the city's four hospitals: Shaare Zedek, Bikur Holim and both campuses of Hadassah University Hospital, at Ein Karem and Mount Scopus.

Police Commissioner David Cohen yesterday ordered the force's alert raised to the highest level.

The bomb went off when bus No. 74, traveling from Givat Shaul to Har Homa, stopped at the station. A woman of 59 who was waiting at the bus stop was critically hurt and died on the way to the hospital.

Another woman, who was also at the bus stop, was seriously injured. The owner of a nearby kiosk was seriously hurt as well, and a yeshiva student of about 18 was moderately injured. Twenty-three others, mostly passengers on the bus, were lightly hurt by shrapnel.

The bomb, consisting of an estimated two kilograms of explosives and metal balls, was apparently hidden in a suitcase placed next to a telephone pole, police said yesterday.

The owner of the kiosk near the bomb site, David Amoyal, called the police moments before the blast to report a suspicious object near the bus station. As he was talking to the police, the bomb exploded.

Jerusalem Mayor Nir Barkat, who visited the injured people in Hadassah Ein Karem yesterday, said Amoyal's alertness "saved lives and prevented a much larger disaster."

An eyewitness told Haaretz that she heard a loud blast close to the central bus station. Seconds later, sirens began to wail and security forces rushed to the scene.

"I heard a blast; my first reaction was to cry," said Haim Halfon, 78, of Kiryat Ye'arim, who was waiting at the bus stop. "I lay on the ground, but apparently God has other plans for me."

Ze'ev Sofer, of the Hatzalah rescue service, was about 100 meters away from the bus stop and one of the first rescue volunteers to arrive at the blast site.

"I was there five or 10 seconds after the blast," he said. "I saw immediately the bomb went off outside the bus. Two buses were hit, but the injured people were at the bus stop. I started treating the woman who was hit the worst. She was evacuated in two or three minutes and I went on to treat the rest."

Jerusalem District Police Chief Aharon Franco, who came to the site, said police were checking whether the blast was connected to a bomb a municipal worker found in a garbage container three weeks ago.

"We know Jerusalem is a city under threat and are always on alert," he said.

Cohen, the police commissioner, said "no suspects have been caught yet. We must wait patiently for the Shin Bet security service and police to work."

"We were not surprised by the attack," he added. "Any terror attack is expected in Israel."

Thousands of people, including radical right-wing activists, gathered at the explosion site. Many started shouting "death to the Arabs" and "death to left-wingers."

A group of municipal sanitation workers who approached were attacked by people shouting "death to the Arabs."

Interior Minister Eli Yishai visited the injured people in hospitals and urged military action. "The combination of what happened in Itamar, the goings-on in the south and the attack in Jerusalem shows ... the terror organizations are raising their head, which requires us to act," he said. "At this stage, the events are not linked, but these acts undoubtedly attest to deliberate planning. It's an escalation and we cannot stand idly by."

The entrance to the city was closed for a few hours as security forces combed the area for other suspicious packages or objects.

Mayor Barkat announced that the Jerusalem international marathon scheduled for Friday will take place as planned. "We must get back to routine quickly," Barkat said, inviting Jerusalem residents and visitors to come to the capital and join the marathon. "Terror strives to disrupt our routine, so the best response is to resume it."