Eleven Palestinians including a 16-year-old were killed and more than 80 wounded by gunfire on Wednesday, the Palestinian health ministry said, when Israeli troops raided the flashpoint West Bank city of Nablus, drawing international appeals for calm.

The Israeli army said it was targeting militant suspects, while top Palestinian official Hussein Al Sheikh described the raid as a "massacre" and called for "international protection for our people".

Before dawn on Thursday Palestinian militants hit back, firing six rockets from Gaza into Israel.

The Israeli army said it intercepted five of them and that the sixth struck an uninhabited area.

Palestinian militant group Islamic Jihad claimed responsibility for the rockets after it called on "resistance forces" to respond to the "major crime" in Nablus.

Two hours later, the Israeli military launched air strikes on multiple targets in Gaza, sending plumes of black smoke into the sky.

The missiles targeted "a weapons factory" and a "military camp", both run by Gaza's Islamist rulers Hamas, the army said in a statement.

United Nations chief Antonio Guterres appealed for calm, warning that West Bank tensions had reached their most dangerous level in years.

"Our immediate priority must be to prevent further escalation, reduce tensions and restore calm," the UN chief said.

"The situation in the occupied Palestinian territory is at its most combustible in years," he added, pointing to "sky high" tensions and the stalled peace process.

- 'Explosions and gunfire' -

The Israeli army said Wednesday's raid had targeted a "hideout apartment" used by suspected militants accused of shootings in the West Bank.

It said one of the wanted suspects was "neutralised", along with two others who had opened fire on troops.

Both sides "exchanged fire" and rockets were also fired on the house by the army, said spokesman Richard Hecht.

Rocks, explosive devices and Molotov cocktails were hurled at the troops, said the army, which said it suffered no casualties.

The Palestinian health ministry said those killed in "the occupation's aggression on Nablus" were aged between 16 and 72.

Hours after the raid, the ministry announced the death of a 66-year-old man from tear gas inhalation.

Wednesday's death toll was the highest since the second Palestinian intifada, or uprising, ended in 2005, surpassing that of an Israeli raid last month in Jenin, another flashpoint city in the West Bank.

Palestinian health officials said 82 people were treated for gunshot wounds, and the Palestinian Red Crescent Society said its medics also treated 250 cases of tear gas inhalation.

Mostafa Shaheen, a Nablus resident, said "soldiers... besieged the whole area" at around 9:30 am (0730 GMT) and that "we kept hearing the explosions and gunfire".

The wounded include Palestine TV journalist Mohammed Al Khatib, who was shot in the hand, his colleague told AFP.

The Islamic Jihad militant group said one of its commanders was killed "in a heroic battle".

The Lions' Den, a Nablus-based militant group, said six of those killed were members of various Palestinian factions.

Hailing the army's "courage", Defence Minister Yoav Gallant tweeted that Israel's "long arm" would reach "any terrorist".

A huge crowd of mourners, including armed men, later gathered in Nablus and the nearby Balata refugee camp for the funerals of 10 of those killed.

- 'Spiralling violence' -

State Department spokesman Ned Price said Washington was "extremely concerned by the levels of violence", while EU foreign policy chief Josep Borrell said the European Union was "deeply alarmed by the spiralling violence".

Borrell called on "all parties" to work towards "restoring calm and... avoid further loss of life".

France reiterated Israel's obligation to respect international humanitarian law and use proportionate force.

Neighbouring Jordan said it would "work intensely with all parties to achieve" calm.

Since the start of this year, the Israeli-Palestinian conflict has claimed the lives of 60 Palestinian adults and children, including militants and civilians.

Nine Israeli civilians, including three children, a police officer and one Ukrainian civilian have been killed over the same period, according to an AFP tally based on official sources from both sides.

US Secretary of State Antony Blinken spoke Saturday with Israeli Prime Minister Benjamin Netanyahu and separately with Palestinian president Mahmud Abbas, calling on both to "restore calm".

Israel has occupied the West Bank since the Six-Day War of 1967.

Last year was the deadliest year in the territory since the United Nations started tracking casualties in 2005.

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