*Netanyahu cuts short US visit
*Hamas leader Ismail Haniyeh's office targeted

Israel launched air strikes in the Gaza Strip on Monday after a rocket attack near Tel Aviv wounded seven people, prompting Prime Minister Benjamin Netanyahu to cut short a visit to the United States.

Netanyahu had threatened strong retaliation for the rocket salvo amid accusations from opponents in a closely contested election, two weeks away, that he has been showing weakness in the face of security challenges from Gaza militants.

"The Israel Defence Forces have begun striking Hamas targets throughout the Gaza Strip," the military said in a statement.

Netanyahu, who arrived in Washington on Sunday for a four-day visit, said he would fly home right after meeting President Donald Trump at the White House.

According to Hamas radio, an Israeli air strike targeted the office of Hamas leader Ismail Haniyeh in the Gaza Strip.

Haniyeh was unlikely to have been in the office, as Hamas routinely evacuates its buildings when expecting Israeli attacks.

An Israeli military spokesman declined to comment on the report.

The Israeli military said Hamas, which rules Gaza, launched the rocket that destroyed a house in Mishmeret, a village north of Tel Aviv.

There was no claim of responsibility for the early morning attack. The military said Hamas fired the rocket from about 120km away, making it the longest-range attack from Gaza causing casualties since a 2014 war.

Palestinian security officials said Israeli warplanes attacked targets across the coastal enclave. Palestinian radio stations and Hamas TV played patriotic songs calling for "resistance" against Israel.

There were no immediate reports of casualties in the Gaza Strip. Many targets were likely to have been evacuated in the hours following Netanyahu's initial warning of retaliation shortly after the rocket strike.

Condemning the attack from Gaza, Trump told reporters with Netanyahu at his side that Israel has the "absolute right" to defend itself.

"Israel will not tolerate this. I will not tolerate this," Netanyahu said about the rocket strike. "And as we speak ... Israel is responding forcefully to this wanton aggression."

Israel's Magen David Adom ambulance service said it treated seven people in the Israeli village, including an infant, a three-year-old boy, a 12-year-old girl and a 60-year-old woman who was suffering from blast injuries, burns and shrapnel wounds.

The Israeli military said it was assigning two brigades to the Gaza area and some reservists were being called up. Reuters witnesses saw troops moving towards the border, where the military also closed several roads to civilian traffic.

"We are prepared for a wide range of scenarios," chief spokesman Ronen Manelis said.

Israeli towns near Gaza and Tel Aviv, Israel's commercial capital, opened bomb shelters in anticipation of rocket strikes.

The rocket attack coincided with tension ahead of the March 30 anniversary of Gaza protests that have included Palestinian attempts to breach the frontier and often lethal Israeli fire.

Gaza authorities have said that some 200 people have been killed by Israeli fire in the protests. An Israeli soldier was killed by a sniper along the frontier.

The protesters demand the right to return to land from which their ancestors fled or were expelled in fighting that accompanied Israel’s founding in 1948.

Israeli-Palestinian peace talks have been frozen since 2014.

The Gaza war that year was the third between Israel and Hamas in a decade. More than 2,100 Palestinians, most of them civilians according to the Gaza health ministry, were killed in seven weeks of fighting. Sixty-six Israeli soldiers and seven civilians in Israel were killed.

Recent Gaza violence has dented Netanyahu's tough-on-security image at a time when he is running neck-and-neck with centrist challenger Benny Gantz, a former armed forces chief.

Netanyahu's election prospects have been clouded by graft allegations against him. He has denied any wrongdoing.

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UN chief concerned , urges restraint

UN Secretary-General Antonio Guterres is "gravely concerned" by the recent developments in Israel and the Gaza Strip and urges all sides to exercise maximum restraint, UN spokesman Stephane Dujarric said.

"Today's firing of a rocket from Gaza towards Israel is a serious and unacceptable violation. We are aware of the latest reports of firing on Gaza," Dujarric said. "We continue to work with Egypt and all concerned parties to try to de-escalate the situation."

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