Israeli troops killed two Palestinians and seriously wounded a third Thursday, the fifth day of an army sweep in this militant stronghold.

Palestinian witnesses said all three men were shot while unarmed. The Israeli military said that in two of the violent encounters, troops fired at Palestinians carrying firebombs, and that the third man was armed.

Later Thursday, the Israeli military reported an exchange of fire in Balata, in which two soldiers were hurt.

Separately, an explosion went off in a house in the camp, the army and Palestinian witnesses said.

The witnesses said that at the time of the blast, a group of medics and journalists had assembled, after being prevented by troops from entering the camp. One medic, Khaled Saragic, said that when a soldier standing next to a jeep heard the blast, he started firing toward medics and journalists, wounding three people.

The military said it was not aware of such an incident.

Since the Balata sweep began Monday, five Palestinians have been killed by army fire, including the two shot dead Thursday. More than 50 Palestinians have been injured by live rounds and rubber-coated steel pellets, Palestinian hospital officials said.

On Thursday, dozens of jeeps patrolled Balata and sealed off the refugee camp from the adjacent city of Nablus. Balata is a stronghold of the Al Aqsa Martyrs' Brigades, a violent offshoot of Palestinian leader Mahmoud Abbas' Fatah Party, and a hideout for weapons dealers.

One of the jeeps broke down on the outskirts of Balata, and several teens began throwing stones at the vehicle, witnesses said. Soldiers opened fire, killing a 19-year-old man. The Israeli military said soldiers fired at the man because he was holding a firebomb.

In another area, Palestinians threw stones at a jeep and soldiers opened fire, hitting one man in the jaw, witnesses said. An AP photographer who heard the shots and rushed to the scene found the man lying on the ground, with blood gushing from a large hole in the jaw. Bystanders quickly bundled him into an ambulance, and hospital officials later reported he was in serious condition.

The Israeli military said the man shot in the jaw apparently had been involved in hurling firebombs, but was not sure if he held one in his hand when hit.

In a final incident, a 22-year-old man was shot and killed by a bullet to the chest while he was standing on his roof in Balata, witnesses said. The military said he was armed when he was shot.