Israel troops backed by dozens of tanks entered the West Bank town of Jenin early on Friday. An Israeli commander quoted by Reuters news agency said it was the biggest security operation since one launched in Nablus in August. Palestinian eyewitnesses said the Israelis were in the town itself and its adjoining refugee camp - they are reported to be carrying out house-to-house searches. It is the first major operation by Israeli forces since a suicide attack on a bus killed at least 15 people, including the two bombers, on Monday outside the town of Pardes Hanna in northern Israel, close to the West Bank.