According to Aljazeera's correspondent, Israeli special forces from what is called the Arabist Unit, disguised as Palestinians in civilian clothing penetrated the area of Jabal abu Dhahira in Jenin and opened fire on a vehicle carrying two resistance fighters on Saturday.
Two fighters were killed as well as a 16-year old youth walking home from school.
An Israeli military source gave a different account saying soldiers had surrounded a house where suspected fighters were planning a bombing.
Israel claims the three died after an exchange of fire with Israeli soldiers.
One of the fighters belonged to al-Aqsa Martyrs Brigades, part of President Yasir Arafat's Fatah faction, and the other to the Islamic Jihad group, the Palestinian security sources said.
Palestinian sources named them as Kamal Tubassi, 30 and Said Hardan, 25.
Israeli occupation toops later shot dead another two Palestinian activists while attempting to arrest them near Jenin, an army source said.
A Palestinian photographer working for an international agency and Aljazeera's correspondent in Jenin, Ali al-Sumodi was also injured by Israeli fire.
Al-Sumodi said he had arrived at the scene of the Abu Dhihaira shooting and donning a helmet and clothing clearly identifying him as a journalist, began filming.
Journalists are not immune to
"The occupation forces saw me and allowed me to film. They did not ask me to leave the area," he said.
About half an hour later, he said he was told to leave and as "I was walking in the street, where there were no clashes, Israeli snipers hit me directly in the nose", al-Sumodi explained.
He said "the soldiers saw me bleeding, but did not offer any help."
"I was shot," he cried and "my colleague also shouted that 'Ali is wounded'".
Al-Sumodi said he ran for about 200 metres to where the ambulances were.
"I think opening fire on me was intentional and is part of a plan to target Palestinian journalists."
"I think opening fire on me was intentional and is part of a plan to target Palestinian journalists"
Aljazeera correspondent in Jenin
Al-Sumodi also said he saw Israeli occupation troops preventing ambulances from reaching other injured Palestinians as well. At least 30 Palestinians have been killed by Israeli forces since Israel assassinated a leader of Hamas group last week.
In other incidents, three Palestinian schoolboys were wounded on Saturday by Israeli fire during clashes with troops in the town of Yabad, west of Jenin, according to a Palestinian security source said who added that soldiers fired on the school.
Yasir Arafat told a crowd that he
would embrace martyrdom
Earlier in the day, Palestinian President Yasir Arafat responded defiantly to new threats against his life by Israeli Prime Minister Ariel Sharon, telling a crowd of supporters he would embrace martyrdom.
"All of us are martyrs-in-the-waiting," Arafat said in the compound of his Muqata headquarters in the West Bank city of Ram Allah, where about 4,000 people chanted they would sacrifice their "blood and souls" for the veteran leader.
Sharon, in comments that could rally support in his right-wing Likud party before its 2 May vote on his Gaza pullout plan, said on Friday he no longer felt bound by a pledge he made three years ago to US President George Bush not to harm Arafat.