Palestinian militants launch military operation, Israel strikes targets ...

The Israeli military has begun striking targets in the Gaza Strip following a series of rocket attacks and an infiltration by Palestinian militants into southern Israel.

The attacks came after weeks of heightened tensions along Israel's volatile border with Gaza, and heavy fighting in the Israeli-occupied West Bank.

Air raid sirens sounded in Jerusalem and residents across the region were ordered to remain indoors as militants fired dozens of rockets into Israel.

A senior Hamas military leader announced the start of a major new military operation on Hamas media, calling on Palestinians everywhere to fight.

"This is the day of the greatest battle to end the last occupation on Earth," said Mohammad Deif, claiming that 5,000 rockets had been launched.

Israel's military said it was on a war footing as Prime Minister Benjamin Netanyahu called an emergency meeting of security officials.

The Israeli military said its forces were operating inside Gaza but gave no details.

At least one Israeli woman was killed, according to emergency services, as ambulance crews were deployed in areas around the Gaza Strip and sirens sounded across Israel, including Jerusalem.

Israeli media reported that gunmen had opened fire on passers-by in the town of Sderot, in southern Israel, and footage circulating on social media appeared to show clashes in city streets.

"A number of terrorists have infiltrated into Israeli territory from the Gaza Strip," the Israeli military said in a statement, adding that residents in the area surrounding the Gaza Strip had been told to stay in their homes.

"The Israeli Defence Forces will defend Israeli civilians and the Hamas terrorist organisation will pay heavy price for its actions," it said.

The sound of outgoing rockets being fired could be heard in Gaza and sirens wailed as far away as Tel Aviv, some 70 kilometres to the north, during an early morning barrage that lasted more than 30 minutes.

Salah Arouri, an exiled Hamas leader, said the operation was a response "to the crimes of the occupation."

He said fighters were defending the al-Aqsa Mosque in Jerusalem and the thousands of Palestinian prisoners held by Israel.

The Palestinian Islamic Jihad group said its fighters were joining Hamas in the attack.

"We are part of this battle, our fighters are side-by-side with their brothers in the Qassam Brigades until victory is achieved," said Islamic Jihad armed wing spokesman Abu Hamza on a post on Telegram.

Authorising the call-up of reservists, Israeli Defence Minister Yoav Gallant said "Hamas made a grave mistake this morning and started a war against the State of Israel."

"IDF soldiers are fighting the enemy at all the infiltration sites," he said in remarks provided by his office. 

A group representing military reservists who had planned to refuse to attend training over their objections to the government's plans to overhaul the judiciary called on reservists to report for duty.

Israel has maintained a blockade over Gaza since Hamas, an Islamic militant group that opposes Israel, seized control of the territory in 2007.

The bitter enemies have fought four wars since then. There have also been numerous rounds of smaller fighting between Israel and Hamas and other smaller militant groups based in Gaza.

The blockade, which restricts the movement of people and goods in and out of Gaza, has devastated the territory's economy.

Israel says the blockade is needed to keep militant groups from building up their arsenals. The Palestinians say the closure amounts to collective punishment.

The rocket fire comes during a period of heavy fighting in the West Bank, where nearly 200 Palestinians have been killed in Israeli military raids this year.

Israel says the raids are aimed at militants, but stone-throwing protesters and people uninvolved in the violence have also been killed. Palestinian attacks on Israeli targets have killed over 30 people.

Reuters/AP