An IDF soldier was moderately wounded on Wednesday afternoon when Palestinians detonated a bomb next to an IDF unit operating in the Kasba of Nablus as troops resumed their operations to track down gunmen in the West Bank city. The soldier, who was performing house-to-house searches with his colleagues, was evacuated to Petah Tikva's Belinson Hospital for medical treatment. Moments after the incident, an 18-year-old Palestinian stone thrower was wounded when he was shot by IDF soldiers also in the city's Kasba region. Earlier in the West Bank city, Palestinians threw a pipe bomb at IDF troops. No one was wounded. Eyewitnesses reported that 50 Palestinians were been arrested or detained for interrogation during the operation. IDF troops had withdrawn on Tuesday but were back at dawn Wednesday, witnesses said. Bulldozers sealed off all entrances to the old city with rubble and jeeps patrolled the streets of much of the city to reinstate a curfew, they said. About 50,000 people were confined to their homes. The army has said the operation was necessary in the city known for its terrorist activity since most of the suicide bombers trying to enter Israel from the West Bank come from Nablus. Thus far, one Palestinian has been killed in the operation, which began Sunday. Also on Wednesday morning, undercover Border Police forces operating in Jenin killed three armed Islamic Jihad terrorists Wednesday morning, including the group's local leader, Ashraf Sa'adi. The other two were known Islamic Jihad operatives Muhammad Abu Nasa and Daoud Jabli. One IDF soldier was lightly wounded in the operation, in which the troops exchanged gun fire with Sa'adi and his men. According to Palestinian witnesses at the scene, the three were sitting in a car when a black car drove up alongside and fired shots. The men in the black car were not wearing any uniforms, they said. Two of the men were killed on the spot and the third, Sa'adi, exited the car and tried to run but was shot down and killed, the witnesses added. The army disputed the witnesses' account, saying troops had tried to arrest Sa'adi in a hospital parking lot, but he opened fire at them. Troops returned fire, killing the three terrorists, the IDF said. Following the operation a spokesman for Islamic Jihad in the Gaza Strip, Abu Ahmad, warned Israel, "This new crime will not pass without tough punishment. "Their blood will be the fuel of our holy battle. And our reaction is coming soon." Islamic Jihad tried last week to carry out a suicide bombing in Israel but the bomber, who was from the Jenin area, was caught. In related news, IDF units operating in other areas of the West Bank overnight Tuesday arrested a total of 25 Palestinians wanted for involvement in terror, the army said. No troops were wounded in the operations.