Israel closed the Gaza Strip's main cargo crossing on Tuesday after militants in the besieged Palestinian enclave launched incendiary balloons into Israeli territory.

"Kerem Shalom Crossing will be closed, with the exception of the entry of essential humanitarian equipment and fuel," from Tuesday, COGAT, the defense ministry unit that oversees the crossings, said in a statement issued late on Monday.

The measure is a response to "the continued launching of incendiary balloons from the Gaza Strip into the territory of the State of Israel," the statement read, adding that the move followed an order by Israel's Defense Minister Benny Gantz.

Explosives tied to balloons and kites first emerged as a weapon in Gaza during intense protests in 2018, when the devices drifted across the border daily, causing thousands of fires in Israeli farms and communities.

In the past week, such balloons have been launched three times from Gaza into Israel, each time triggering retaliatory strikes against Hamas positions.

Hamas also fired several rockets into the sea on Monday after repeated exchanges of fire with Israel in recent days, Palestinian security sources and eyewitnesses said.

Israel believes that the balloons are sent by militant opposition groups in Gaza but it holds Hamas, a Palestinian movement that runs Gaza, responsible for the launchings.

"The IDF (Israel Defense Forces) and the State of Israel will respond firmly to any violation of our sovereignty and our citizens," the statement warned, adding that the balloons "harm the residents of the Gaza Strip, the development of the economy and attempts to improve the civilian situation of its residents."

Local Israeli media reported that balloons attached to incendiary devices have caused more than 30 fires around border communities, without causing casualties.

Commentators on Palestinian and Israeli media said the balloons often aim to pressure Israel to allow the transfer of Qatari money to Gaza amidst an escalating financial and humanitarian crisis in the Palestinian enclave.

Hamas and Israel have fought three wars since 2008. Over the past months, both sides kept an unofficial ceasefire, while sporadically clashing with rockets, mortar fire or incendiary balloons.

(With input from agencies)