Jerusalem ? An 18-year-old Palestinian woman blew herself up at the entrance of a Jerusalem supermarket Friday, killing two other people and injuring about 20.

The blast at a strip mall in Kiryat Yovel, a working class Jewish neighborhood in the southeastern part of the city, sprayed glass and debris onto the sidewalk.

Witnesses said the three torn bodies lay near the entrance of the SuperSol supermarket in a heap of debris: charcoal from bags that were on sale, pools of white house paint from a destroyed store display and flowers that a vendor had been selling.

A man covered in the white paint sat on the steps outside the shopping center, crying and hugging two small children.

Police spokesman Gil Kleiman said the teen-age bomber set off her explosives as a security guard tried to keep her out of the store. The security guard’s efforts “saved a large number of lives,” Kleiman said.

The bomber and two people, a man and a woman, were killed, Kleiman said. He would not say if the security guard was among the dead.

Hanna Cohen, a witness who spoke to Israel Radio, said she was about to enter the store when there was “was a huge blast, and I saw people flying all around, arms and legs.”

Avraham Ben-Yakov, a 38-year-old doctor, had gone to the store with his wife to do some weekend shopping. Ben-Yakov remembered telling the security guard as they entered that he was doing a good, important job.

The woman bomber was just a few steps behind the doctor.

“I saw a very intense explosion with dark smoke,” Ben-Yakov said. “People started running, crying.” Rushing to help the wounded, Ben-Yakov found the young security guard barely breathing, both of his legs severed. “He lost all of the blood,” he said.

As explosives experts went through the wreckage, they found an unexploded mortar shell that the bomber had carried with her.

The Al Aqsa Brigades, a militia linked to Palestinian leader Yasser Arafat’s Fatah movement, claimed responsibility in a phone call to The Associated Press. The militia identified the bomber as Ayat Akhras from the Dheisheh refugee camp in Bethlehem.

Some earlier reports said the bomber was 16, but documents provided by her family showed she was 18.

As word of the bombing spread through the camp, some residents celebrated, handing out candy and firing guns into the air.

Palestinian militants have carried out dozens of bomb attacks during the 18 months of Mideast fighting. There have been about 50 suicide bombings during the Palestinian uprising, and Friday’s attack was the second such attack carried out by a woman.