Israeli air strikes on Gaza killed three Islamic Jihad militant group leaders early Tuesday and left 10 others dead, including several children, according to officials in the Hamas-controlled Palestinian territory.
Islamic Jihad vowed to "avenge" the deaths after the pre-dawn raid in which more than 40 Israeli jets hit targets for nearly two hours in the crowded coastal enclave from just after 2:00 am (Monday 2300 GMT).
The ministry said that women and children were among the dead, publishing a list of names without ages or detailing any affiliations.
An AFP journalist in Gaza saw the top of a building on fire immediately after the strikes as well as ambulances evacuating victims.
The Israeli army claimed it had targeted three leaders of Islamic Jihad, which it considers a terrorist organisation, and had hit "weapon manufacturing sites" belonging to the group.
Army spokesman Richard Hecht told journalists the force "achieved what we wanted to achieve" in the overnight strikes, which he said involved 40 aircraft.
Islamic Jihad confirmed three senior officials were killed, naming them in a statement as Jihad Ghannam, secretary of the Al-Quds Brigades military council, and Khalil al-Bahtini, also of the council and commander of the military wing in northern Gaza.
The third, Tareq Ezzedine, was described by Islamic Jihad as "one of the heads of military action" in the occupied West Bank who operated from Gaza.
In Rafah, in the south of the Gaza Strip, an AFP photographer saw the body of a man identified as Ghannam.
"We mourn the leaders and their wives and a number of their children who were killed in a cowardly Zionist crime," Islamic Jihad said in a statement, vowing "the blood of martyrs will increase (the) resolve" of the movement.
An AFP photographer saw a boy's body in the morgue of Gaza City's Shifa hospital, where mourners had gathered.
Asked by journalists about child casualties, Hecht said: "If there were some tragic deaths, we'll look into it."
Explosions from air strikes, which began a little after 2 am (2300 GMT), could be heard for nearly two hours, according to AFP journalists.
The attack by Israel came less than a week after Islamic Jihad announced a truce around Gaza - brokered with help from Egypt - following a flare-up in violence after the death in Israeli custody of a hunger striker with ties to the militant group.
On Tuesday, Islamic Jihad said Israel had "scorned all the initiatives of mediators" and vowed it would "avenge the leaders" killed in the latest air strikes.
In separate statements detailing each of the Islamic Jihad figures killed, the Israeli military claimed that Ghannan as "one of the most senior members of the organisation" who coordinated weapons and money transfers between the group and Hamas.
Bahtini was "responsible for the rocket fire toward Israel in the past month", Israel claimed.
Ezzedine was recently "planning and direction (sic) multiple attacks against Israeli" civilians in the West Bank, where he was from, and which has been occupied by Israel since the Six-Day War of 1967.
He was sentenced to 25 years in prison by Israel for his involvement in suicide attacks in the 2000s, before being freed in a 2011 prisoner exchange and transferred to Gaza, according to the Israeli army.
An Islamic Jihad source told AFP that Ezzedine was part of a delegation from the group due to travel to the Egyptian capital Cairo for a Thursday meeting, which has been cancelled in the face of the air strikes.
Hecht said the military was "looking where this thing will develop", with the army instructing Israeli residents within 40 kilometres (25 miles) of the Gaza border to stay near bomb shelters until Wednesday evening.
The army subsequently said its troops had entered Nablus in the northern occupied West Bank, with residents telling AFP they heard explosions during the raid.
In a statement, Hamas chief Ismail Haniyeh said, "Assassinating the leadership in a treacherous operation will not bring security to the occupier, but instead greater resistance".
The militant group's spokesman, Hazem Qassem, warned that Israel "bears responsibility for the repercussions of this escalation".
Israel and Gaza's armed resistance groups have fought multiple wars since Hamas took control of the Palestinian enclave in 2007.
A three-day conflict in Gaza last August left 49 Palestinians and no Israelis dead, with Cairo playing a key role in securing a truce.
Tuesday's deaths bring to 120 the number of Palestinians killed by Israel so far this year.
Nineteen Israelis, one Ukrainian and one Italian have been killed over the same period, according to an AFP count based on official sources from the two sides.