Ten Palestinians, including an elderly man and several militants, have been killed during a raid by Israeli forces in the occupied West Bank, witnesses and Palestinian health officials say
Explosions and gunfire sounded as troops entered the heart of Nablus, triggering armed clashes with gunmen.
The Israeli military said its forces surrounded a building while looking for "wanted terror suspects".
The men were shot and killed after they opened fire at the troops, it added.
The troops also shot back after coming under fire from other armed men and having explosives, petrol bombs and stones thrown at them during the clashes, according to the military.
The Palestinian health ministry said 72-year-old Adnan Saabe Baara was among those killed during the raid.
Video footage showed a body in a street next to bags of bread, in what is usually a busy market area of the old city.
A 61-year-old man called Abdul Hadi Abdul Aziz Ashqar and a 16-year-old boy Mohammad Farid Shaaban also died, according to the health ministry.
More than 100 other Palestinians were also wounded by gunfire. Seven of them are in a critical condition in local hospitals.
The Israeli military named the three militants who were the targets of the raid as Mohammed Abdul Fattah, 23, a member of Palestinian Islamic Jihad, and Walid Dkhail, 23, and Hussam Isleem, 24, of the Lion's Den group.
The military said they were suspected of carrying out previous shooting attacks, including one last October that killed an Israeli soldier, and of planning others in the near future.
A spokesman for Palestinian President Mahmoud Abbas said he condemned the raid and held Israel's government responsible for "this dangerous escalation, which is pushing the region toward tension and an explosion".
The Palestinian militant group Hamas, which controls the Gaza Strip, warned that it was "monitoring the escalating crimes conducted by the enemy against our people in the occupied West Bank and is running out of patience".
Nablus and nearby Jenin have been the focus of search, arrest and intelligence gathering raids that Israel has intensified over the last year amid a spate of deadly Palestinian attacks.
This latest one comes despite reports this week of an understanding brokered by the US aimed at calming tensions.
So far this year, at least 50 Palestinians - including militants and civilians - have been killed, while 11 people have been killed in Palestinian attacks targeting Israelis.