During the incursion one soldier was lightly wounded when an explosive device was thrown at the troops, the army said.
Following a Feb. 8 declaration by Palestinian and Israeli leaders to end the violence Israel has cut back its raids on Palestinian towns and villages, saying they would only go in in cases where there was an immediate danger of an attack being launched.
Military officials, speaking on condition of anonymity, said the eight men were militants from the violent Islamic Jihad (search) group and were attempting to build home made rockets.
Residents said three of the men, arrested in a village on the outskirts of the town, were members of Palestinian security forces. The other five were not known militants, they said.
Militants in the Gaza Strip have fired hundreds of homemade rockets and mortars ant nearby Jewish settlements and Israeli towns, but those in the West Bank have not yet been able to duplicate the technology.
As part of the Feb. 8 agreements Israel promised to hand over control of five West Bank towns to Palestinian security. But on Sunday Defense Minister Shaul Mofaz said he had ordered a postponement in handing over Qalqiliya, the third of five Palestinian towns due to be transferred to Palestinian security. He charged that the Palestinians were not carrying out their security pledges in the first two, Jericho and Tulkarem.
Jenin is not one of the towns scheduled for a handover.