Israel warned Hamas Thursday against any escalation in violence, reinforcing its border with Gaza amid continued Palestinian rocket fire and heightened tensions following the murder of three Israeli youths and a Palestinian teenager.
"We are looking for calm, not escalation, but if Hamas chooses to act against us, we shall be ready," armed forces chief Lieutenant General Benny Gantz said in remarks tweeted by the army.
But in Gaza, the Ezzedine al-Qassam Brigades, the military wing of Hamas, warned Israel to wind down its Gaza air strikes and widespread West Bank arrests -- mainly of Hamas members.
"What the enemy is doing in the West Bank and Gaza... adds fuel to the fire of confrontation," spokesman Abu Obeida told a press conference.
"Idiotic measures by your leaders will be enough for us to turn your localities and sites...into embers."
The war of words came as Palestinians in east Jerusalem hurled rocks and fireworks at Israeli police and sent burning car tyres rolling along streets in a second day of protests over the kidnap and murder of Mohammed Abu Khder, a local 16-year-old.
Many believe the boy's death was in revenge for the abduction and murder in the West Bank last month of the three Israeli teens, whose bodies were found on Monday.
Israel police say the motive for Abu Khder's killing is still unclear, and have not said how he died.
But the family's lawyer told AFP the boy's body had been burnt "beyond recognition."
Police spokesman Micky Rosenfeld told AFP he would be buried on Friday afternoon.
Hamas, blamed by Israel for the kidnap and murder of the Israelis, said it held Israeli Prime Minister Benjamin Netanyahu's government directly responsible for the killing of Abu Khder.
"You will pay the price for your crimes," it said.
Amid the growing tensions, army spokesman Lieutenant Colonel Peter Lerner said "we are moving and we have moved forces in order to serve defence activities and forward preparation, but we have no interest in escalation."
The reinforcements were reserve officers at "headquarter level, not in the field", Lerner said, and were a purely defensive measure.
But an AFP photographer saw tanks arriving at a kibbutz near the border.
Israeli warplanes pounded targets inside Gaza and militants hit back with 21 rockets.
Netanyahu denounced Abu Khder's killing as "despicable" and urged both sides "not to take the law into their own hands."
One of the families of the three murdered Israelis described it as a "horrendous act."
Palestinian president Mahmud Abbas demanded that Netanyahu act against revenge attacks and called for Abu Khder's killers to be caught and punished.
Four Israeli soldiers who allegedly used social media to call for revenge and to "annihilate terrorists" were jailed for 10 days by the military.
Outgoing Israel President Shimon Peres issued a plea for restraint.
"People who are engaged in incitement are not always aware where it can lead, to more sorrow, to more dangers," he said in a statement.
Since Wednesday midnight, 20 projectiles have been fired on Israel from Gaza, the army said, with one soldier lightly wounded in one incident.
In response, Israeli warplanes hit the Gaza Strip in the afternoon after local and Israeli sources said 11 Palestinians were wounded in strikes overnight.
- Witnesses on teen's 'abduction' -
Witnesses told AFP they saw Abu Khder being forced into a black Honda Civic by "two Israelis" with a third in the driving seat. It then drove off at high speed, evading two cars which tried to follow.
The killing drew condemnation from around the world, including from the UN and the International Committee of the Red Cross, which said the abduction and murder of civilians "must stop now."
A rally in central Tel Aviv called by leftist Israeli groups to protest against violence and counter calls for revenge had a poor turnout, with witnesses estimating the crowd at no more than 2,000.
Police said that "hundreds" attended a similar event outside Netanyahu's official residence in Jerusalem.
Tensions have soared since June 12 when the three Israelis disappeared in the West Bank, triggering a vast search and arrest operation across the territory.
Their bodies were found on Monday, but the hunt for the killers continues, with troops arresting another 13 Palestinians on Wednesday night, the army said.