Palestinian militants fired a rocket from Gaza into Israel Saturday without causing any casualties, the army said, as a surge in violence grips the occupied West Bank.
There was no immediate claim for the attack, the first in a month according to the army.
However, one of Gaza's larger armed factions, Islamic Jihad, had threatened to retaliate after Israeli troops killed two of its leaders in the West Bank town of Jenin on Thursday.
Witnesses said the Israeli army swiftly riposted by firing on two observation posts east of Gaza City, operated by the territory's Islamist rulers Hamas.
The rocket attack came as a surge in bloodshed in the occupied West Bank sparked international criticism of the Israeli army for its use of lethal force against Palestinian civilians.
Criticism has focused on the killing of Ammar Hadi Mufleh, 22, in disputed circumstances in the town of Huwara, just south of Nablus, on Friday.
United Nations Middle East peace envoy Tor Wennesland said he was "horrified" by the killing "during a scuffle with an Israeli soldier".
The European Union said it was "greatly concerned about the increasing level of violence" which had seen 10 Palestinians killed by Israeli security forces in recent days.
"Such unacceptable facts must be investigated and there must be full accountability," EU foreign policy chief Joseph Borell said.
"Under international law, lethal force is only justified in situations in which there exists a serious and imminent threat to life".
According to the Israeli version of events, Mufleh tried to force open the door of an Israeli couple's car before stabbing a border policeman.
A senior border police officer then shot Mufleh dead, saying that the Palestinian had made a grab for his weapon.
Palestinian municipal official Wajeh Odeh told AFP the shooting followed "a quarrel".
"An Israeli soldier pushed the Palestinian to the floor and shot him from zero distance," Odeh said.
The Israeli foreign ministry responded angrily to the criticism.
"This reaction is a total distortion of reality," it tweeted in English. "This is NOT a 'scuffle' -this is a terror attack!"
Outgoing Israeli Prime Minister Yair Lapid said he fully supported the border police officer's decision to open fire "to save lives".
"Our security forces will continue to act resolutely against terrorism," he said.
At least 145 Palestinians and 26 Israelis have been killed in violence in Israel and the West Bank, including annexed east Jerusalem, this year, the heaviest toll since 2015.