Israel launched air strikes in the Gaza Strip on Monday.
The Israel Defence Forces striked Hamas targets throughout the Gaza Strip.
Hamas fired a rocket from Gaza that destroyed a house and caused casualties in Mishmeret, a village north of Tel Aviv.
The Israeli warplanes attacked targets across the coastal enclave.
Hamas leader Ismail Haniyeh said his group will respond if Israel retaliates too forcefully to an overnight rocket strike.
Police and security installations were evacuated and hospitals in Gaza were on alert.
Hamas leaders went into hiding.
The U.S. President Donald Trump condemning the attack from Gaza said Israel has the absolute right to defend itself.
Israeli Prime Minister Benjamin Netanyahu said, Israel will not tolerate this and is responding forcefully to the aggression.
The Israeli military said it was assigning two brigades to Gaza and preparing for a wide range of scenarios.
Troops were moving towards the border, where the military also closed several roads to civilian traffic.
Gravely concerned by the recent developments in Israel and the Gaza Strip, United Nations Secretary-General Antonio Guterres urged all sides to exercise maximum restraint.