Two Palestinian intelligence officers have been killed by Israeli special forces during a raid in the occupied West Bank, Palestinian officials say.
The Israeli forces, some undercover, entered Jenin overnight to arrest two Palestinians suspected of recent attacks, according to Israeli media.
The Palestinian officers were shot dead after they witnessed the raid and reportedly opened fire at the Israelis.
A Palestinian man identified as one of the suspects was also killed.
The West Bank-based Palestinian Authority (PA) co-ordinates security with Israel and clashes between their forces during such operations are rare.
Palestinian officials named the two officers who were killed as Adham Alawi and Taysir Issa. Both were members of the PA's military intelligence department in Jenin.
A third officer was critically wounded in the firefight as well, according to the official Palestinian Wafa news agency.
The Israeli Border Police said in a statement that members of its special anti-terrorism unit, Yamam, entered Jenin in the early hours of Thursday to arrest two Islamic Jihad operatives suspected of shooting at Israeli soldiers in the West Bank, who were identified as Jamil al-Amouri and Wisam Abu Zeid, Israel's Haaretz newspaper reported.
An exchange of fire broke out when the Yamam forces tried to arrest the suspects and other armed individuals at the scene opened fire at them, the statement said. The Yamam forces returned fire and shot three of the armed individuals, it added.
"It appears that the unit they fired on was undercover," an Israeli security source told Reuters news agency.
"Our forces fired back, apparently thinking that the shooting from the Palestinian security men was part of the clash [with the suspects]."
Wafa said the Yamam forces had attempted to detain the Palestinian suspects outside the PA military intelligence department's headquarters in Jenin.
Jamil al-Amouri was also killed during the firefight, while Wisam Abu Zeid was reportedly wounded.
Wafa cited a spokesman for PA President Mahmoud Abbas, Nabil Abu Rudeineh, as saying he strongly condemned "the dangerous Israeli escalation".
Mr Abbas held "the Israeli government responsible for this escalation and its repercussions", and called on the international community "to provide protection for the Palestinian people", he added.
The incident comes just weeks after the end of an 11-day conflict between Israel and Palestinian militant groups in Gaza. At least 256 people were killed in Gaza, according to the UN, and 13 people were killed in Israel.