Israeli warplanes have carried out a series of airstrikes at militant sites in Gaza, the first such raids since a shaky ceasefire ended the war last month.
There were no immediate reports of casualties in the airstrikes today.
They targeted facilities used by Hamas for meetings to plan attacks, Israel's military said, blaming the militant group for any act of violence emanating from Gaza.
Israeli media reported the military was on heightened alert in the occupied West Bank and along the Gaza frontier.
Batteries of Israel's Iron Dome rocket-defence system were seen deployed near the southern town of Netivot, near the Gaza border, as a precaution.
Defence Minister Benny Gantz met with the military chief of staff, the police commissioner and other senior security officials. He "underscored the need to avoid friction and protect the personal safety of ... Jews and Arabs alike," his office said.
United Nations deputy spokesman Farhan Haq said UN officials have urged all sides to avoid "provocations" in order to solidify the informal cease-fire that halted the Gaza war.
The airstrikes were launched today after Palestinians in Gaza released incendiary balloons that caused at least 10 fires in southern Israel.
Later, hundreds of Israeli ultranationalists, some chanting "Death to Arabs," paraded in east Jerusalem in a show of force that threatened to spark renewed violence,
Prime Minister Mohammad Shtayyeh, of the internationally backed Palestinian Authority in the West Bank, called the march an "aggression against our people".
In neighbouring Jordan, the Foreign Ministry issued a statement condemning the march as "unacceptable," saying it undermined efforts to reduce friction between Israel and the Palestinians.
The new raising of tensions come just days after a new Israeli government took power.
New prime minister, Naftali Bennett, a hardline Israeli nationalist has promised a pragmatic approach as he presides over a delicate, diverse coalition government.