Israeli forces killed three unarmed Palestinians, including a senior Al-Aqsa Martyrs' Brigades leader, and wounded one in Qalqilyah after spotting them in the center of the West Bank city before dawn Friday. The victims were identified as Muhammad Abd al Hafizh Nazal, 30, Muahmmad Kamel Nazal, 23, and Abd a Rahman Wasef Nazal, 22. Israeli sources said one of the men killed was Al-Aqsa Martyrs' Brigades second in command and the two other men were reportedly associated with the Fatah movement. Palestinian medical sources said two of the dead were shot directly in the heart while the third was hit in the head. The Al-Aqsa Martyrs' Brigades leader in the city, Atef Sha'aban, was moderately injured in the shooting and evacuated from the scene by a Red Crescent ambulance. He is reported to be hospitalized in serious condition. A fourth Palestinian was reportedly killed in Talouza, north of Nablus. Israeli troops, backed by a helicopter raided the village. According to Israeli reports, Palestinians opened fire, drawing return fire that killed one man and wounded another. The Israeli army said that the fatality was a wanted Hamas member. However, Palestinians said the man killed in the incident was a bystander. They identified him as Dr. Yasser Ahmed Abu Limon, 32, who worked as a lecturer at the Arab American University, Jenin. Also Friday, Palestinians reported Israeli military activity near the West Bank city of Ramallah. On Thursday, Israeli soldiers killed six Palestinians in the West Bank and Gaza Strip. **Sharon tells Bush: Commitment not to kill Arafat - not valid*** Israel's Prime Minister Ariel Sharon informed U.S. President George W. Bush at their meeting last week that his commitment not to kill Palestinian Authority Chairman Yasser Arafat is no longer valid, Sharon disclosed in an interview aired on Israel's Channel Two TV on Friday evening. According to Sharon, he told the American president that at their first meeting, three years ago, he accepted Bush's request not to "inflict physical harm" on Arafat. The prime minister said that he told Bush last week that he understands the problems involved, but that he is not longer obligated to that agreement. Sharon did not disclose what Bush's response was. Shortly after Sharon's comments, the U.S. State Department said it stood by its opposition to the assassination of Arafat. "Nothing has changed in the U.S. position and I will look at the statement and see what we have to say," State Department spokesman Richard Boucher told reporters. Nabil Abu Rdeneh, a close aide to Arafat, warned that Sharon's "dangerous statements ... could push the whole region into tremendous danger." "We call upon the U.S. administration to clarify its position on these statements and to bear its responsibility toward this escalation," he said. **PHOTO CAPTION*** President Bush and Prime Minister Sharon are shown at the White House, April 14. (Reuters)