JERUSALEM - Israel warned Hamas Thursday against any escalation in violence, reinforcing its Gaza border amid continued rocket fire and heightened tensions after 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.
The Ezzedine al-Qassam Brigades, Hamas's military wing, 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 reporters.
"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 burned car tyres on a second day of protests over the kidnap and murder of local 16-year-old Mohammed Abu Khder.
Many believe he was killed in revenge for the abduction and murder in the West Bank last month of the three Israeli teenagers whose bodies were found on Monday.
Israeli police say the motive for Abu Khder's killing is still unclear, and have not said how he died.
But the family lawyer told AFP the boy's body had been burnt "beyond recognition".
After an autopsy Abu Khder will be buried following traditional Friday prayers, the first of Islam's holy month of Ramadan.
'You will pay'
Hamas, blamed by Israel for the kidnap and murder of the Israelis, said it held Prime Minister Benjamin Netanyahu's government directly responsible for Abu Khder's killing.
"You will pay the price for your crimes," it said.
As tensions rose, 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 purely defensive.
However, an AFP photographer saw tanks arriving at a kibbutz near the Gaza border.
"We are prepared for two possibilities in the south," army radio quoted Netanyahu as telling a July 4 reception at the US ambassador's residence.
"That the fire at our communities will stop and our activities will also stop, or that the fire at our residents of the south will continue and then the reinforced troops which are in place will act forcefully."
Israeli warplanes pounded targets inside Gaza on Thursday and militants fired 34 rockets into Israel, the army said.
It said another two were intercepted by the Iron Dome defence system and four more failed to clear the border.
Netanyahu denounced Abu Khder's killing as "despicable" and urged both sides "not to take the law into their own hands".
Four Israeli soldiers who allegedly used social media to call for revenge and to "annihilate terrorists" have been jailed for 10 days.
Outgoing Israeli President Shimon Peres in a statement called for restraint.
"People who are engaged in incitement are not always aware where it can lead, to more sorrow, to more dangers," he said.
Witnesses saw '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 "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.
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.
Separately, the International Monetary Fund on Thursday said the economy in the West Bank and Gaza was weakening, urging Israel to lift restrictions on the Palestinians.
IMF mission chief Christoph Duenwald said the global donor community needed to step up to help fill a "sizeable" financing gap this year for the authority.