A Palestinian homicide bomber -- and mother of two -- blew herself up Wednesday at the main crossing between Israel and the Gaza Strip (search), killing four people and injuring seven, emergency officials said.

Authorities believe this was the first mother to act as a homicide or suicide bomber. She was identified as Hamas member Reem Al-Reyashi, 22, of Gaza. Family members said she had a 3-year-old boy and 1-year-old girl.

Israel Radio reported that the four dead were Israelis. Four of the wounded were Palestinians, the army said.

The bomber set off the explosion shortly before 10 a.m. at the Erez Crossing (search), where 4,000 Palestinian laborers pass every day through a network of fences and security checks to go from the Gaza Strip to jobs in Israel.

Palestinian witnesses said the bomber was a woman waiting on line to pass through to the Israeli side.

A witness identifying herself as Amena, 42, said four Palestinian women went into a security office at the border crossing. The explosion occurred inside as she was waiting outside, she said.

"I heard soldiers screaming. The blast was very strong, and I saw one of the women, the last one who went into the room, bleeding from her legs," she said.

The bomber told soldiers at the crossing point that she would set off a metal detector, because she had an implant from surgery to repair a broken leg. She was then ushered to a special room for a security search, said Maj. Sharon Feingold, a military spokeswoman.

Another witness, who declined to be named, said a woman waiting with the laborers was walking strangely. When the witness offered to help the stranger, the woman brushed her off. The bomb went off shortly afterward.

Wednesday's homicide bombing was the first since a Christmas Day attack at a bus stop outside Tel Aviv that killed four.

The Islamic militant group Hamas (search) and the Al Aqsa Martyrs' Brigades (search), linked to Palestinian leader Yasser Arafat's Fatah movement (search), issued a joint claim of responsibility, according to Lebanon's Al-Manar satellite television station.

The two groups said they worked together to carry out this attack.

Hamas said it sent a woman for the first time because of growing Israeli security "obstacles" facing its male bombers, Reuters reported. Hamas spiritual leader Sheik Ahmed Yassin said the use of a female bomber was unique, but added that holy war "is an obligation of all Muslims, men and women."

Smiling at times in a videotape that showed her cradling a rifle, Al-Reyashi said she had dreamed since she was 13 of "becoming a martyr" and dying for her people.

"It was always my wish to turn my body into deadly shrapnel against the Zionists and to knock on the doors of heaven with the skulls of Zionists," said Reyashi, wearing combat fatigues with a Hamas sash across her chest.

"God gave me two children and I loved them so much. Only God knew how much I loved them," she said.

Palestinian Prime Minister Ahmed Qureia didn't condemn the attack, saying that continued Israeli attacks and restrictions on the Palestinians are leading "to more escalation on both sides."

After the blast, soldiers forced everyone out and shut down the Gaza crossing, witnesses said. A government spokesman suggested the crossing would remain closed.

"Israel allows Palestinian workers to come into Israel. And the Palestinian terrorist organizations took this opportunity in order to kill as many people as possible," said Avi Pazner. "I presume that we will have to take measures in order to prevent that ... It's too early to say exactly what measures we will take."

The seven wounded people were being evacuated to hospitals, according to Moshe Vaaknin, an official with the Magen David Adom rescue services.

Erez has been the target of occasional attacks during the past three years of violence. On June 8, three Palestinian gunmen from different militant groups killed four Israeli soldiers in a coordinated attack there. Soldiers returned fire, killing the gunmen.

On Oct. 14, three American security guards were killed in the Gaza Strip just south of Erez when a Palestinian set off an explosive device at a passing diplomatic convoy.

The Gaza Strip is surrounded by an Israeli security barrier. In the past three years of fighting, only one of the more than 100 homicide bombers has infiltrated Israel from the Gaza Strip.

Islamic Jihad, the other main Islamic fundamentalist group leading attacks against Israelis, and the secular Al-Aqsa Martyrs Brigade have used women for homicide attacks in the past. But Hamas, the largest group, has until now stayed away from the tactic.

Israeli soldiers usually concentrate more on Palestinian men as potential attackers.

The violence follows a West Bank ambush late Tuesday in which Palestinian gunmen killed a Jewish settler in a car at the entrance to the Talmon settlement near the West Bank city of Ramallah. The 28-year-old victim was the father of five, including triplets born two months ago.

The Al-Aqsa Martyrs' Brigades claimed responsibility.

Earlier Tuesday, Israeli troops killed a Palestinian gunmen in a firefight along the Gaza-Egypt border, the army said. The army said the soldiers were returning fire.

The Associated Press contributed to this report.