A 53-year-old woman was killed and several others wounded in air strikes on the Gaza Strip as Israel and Palestinian armed groups engaged in one of the worst exchanges of fire since the 2014 Gaza war.

Gaza Strip Health Ministry spokesman Ashraf al-Qedra said that the woman, identified as Zeina Al Omor, had been killed and several others injured by shrapnel in the southern Gaza city of Khan Yunis.

Israel launched the first strikes in southern Gaza late on Wednesday in response to mortar attacks on Israeli troops along the border. 

Early on Thursday, it launched strikes on four targets in northern Gaza and another four in the south later in the day.

On Thursday, the Islamic Jihad group claimed responsibility for firing five mortar shells at the Israeli ground troops operating near the Gaza-Israel border fence.

It said it was the first time since the 2014 Gaza war that it had done so.

'Clearing border area'

The Israeli military said that during ongoing searches along the Gaza-Israel border, it had found a tunnel running underneath the southern Gaza border at a depth of 27-29 metres.

It was not yet clear how long it was, but the military said it probably reached far into Israel.

Since the 2014 war, Hamas, the movement in de facto control of the Gaza Strip, had "tolerated" Israeli troops entering 100 metres into the Gaza Strip while clearing the border area, an Israeli military spokesman said.

But this time, Israeli troops digging there came under mortar fire, Lieutenant-Colonel Peter Lerner said. It was the second tunnel uncovered by Israel in one month.

One target struck by Israel early on Thursday was a goldsmith workshop in southern Gaza City, residents said. Israel says it has intelligence indicating that workshops are used to produce weapons.

Israel and Hamas accused each other of raising tensions over the volatile territory.

Sources close to Hamas, who spoke on condition of anonymity, said that Egypt had intervened between Hamas and Israel to defuse the growing tension.

Musa Abu Marzooq, a top Hamas leader based in Qatar, wrote on his Facebook page in Arabic that the two sides had accepted an Egyptian call to return to a fragile ceasefire that has largely remained in place since the 2014 Gaza war.

Israeli Prime Minister Benjamin Netanyahu convened his security cabinet for Friday morning to discuss the latest flare-up.

Israel ended its permanent military presence in the Gaza Strip in 2005 in what it called the "Gaza disengagement". 

However, the area remains effectively occupied as Israel retains control of its airspace, seafront and all vehicle access, blocking trade and free movement for the territory's nearly two million residents. 

Source: Al Jazeera and agencies