Three Palestinian militant groups on Saturday vowed to retaliate against Israel after its army killed three militants in Jenin refugee camp overnight. In a joint statement, Hamas' military wing al-Qassam Brigades, Fatah's al-Aqsa Martyrs' Brigades, and Islamic Jihad's al-Quds Brigades threatened a "painful" retaliation against Israel.The statement also accused the Palestinian Authority of complicity in the killings.Three Palestinian militants were killed and several others were injured early Saturday during clashes with Israeli troops  who raided Jenin refugee camp in the northern West Bank, Palestinian security sources said.The three were identified as Hamza Abu al-Haija, a 22-year-old leader of al-Qassam Brigades , Mahmoud Abu Zeina, a 17-year-old member of al-Quds Brigades, and 22-year-old Yazan Mahmoud Basim Jabarin of al-Aqsa Martyrs' Brigades. An earlier Hamas statement said that PA security services had summoned and detained al-Haija several times before.A spokesman for Palestinian president Mahmoud Abbas denounced the killings, describing them as part of "systematic Israeli policy aimed at destroying everything." Nabil Abu Rdeina said that Israel escalated its "attacks against citizens." He urged the US administration to take action before peace talks collapsed.