The Palestinian Islamist group Hamas, which Israel has vowed to destroy after it launched a shock attack on Israel Saturday that killed more than 1,200 people, has ruled the Gaza Strip since 2007.
Here is what we know about the top leaders of the militant organisation which Israeli Prime Minister Benjamin Netanyahu has likened to the Islamic State group.
Ismail Haniyeh, the politician:
The 60-year-old Haniyeh was elected head of the Hamas political bureau in 2017 to succeed Khaled Meshaal, but was already a known figure in 2006 when he became Palestinian prime minister following an upset victory by Hamas in that year's parliamentary election.
But ties with the Fatah movement of Palestinian president Mahmud Abbas were short-lived and in 2007, Hamas took full control of the Gaza Strip after violently ousting the president's loyalists.
Considered a pragmatist, Haniyeh lives in voluntary exile, splitting his time between Turkey and Qatar.
He has long campaigned for a reconciliation between the armed resistance against Israel and a political stance within Hamas, which is blacklisted as a terrorist group by the European Union and the United States.
Haniyeh is said to maintain good relations with the heads of the various Palestinian factions, including rival ones.
In his youth, the Hamas leader, who is known for his calm, was a member of the student branch of the Muslim Brotherhood at the Islamic University of Gaza.
He joined Hamas in 1987 when the militant group was founded as the first Palestinian intifada, or uprising, broke out against Israeli occupation, lasting until 1993.
During that time Haniyeh was imprisoned by Israel several times, and then expelled to south Lebanon for six months.
In footage broadcast by Hamas-linked media on Saturday, Haniyeh is seen watching images on television of the unfolding Hamas attack on Israel, before joining other Hamas leaders in a prayer to "thank Allah for this victory".
Mohammed Deif, the 'chief of staff'
The elusive Deif, who heads Hamas's armed wing, the Ezzdine al-Qassam Brigades, is Israel's public enemy number one and a man they tried to assassinate at least six times and on the US list of "international terrorists" since 2015.
Considered by Hamas as the group's "chief of staff", Deif is the one who announced in an audio message the start of the Hamas attack on Israel dubbed "Al-Aqsa Flood".
In the recording Deif is heard saying that "the positions and fortifications of the enemy have been targeted by 5,000 rockets and shells during the first 20 minutes" of the attack.
Hamas which released the audio message also posted a picture of Deif in the shadow, as it usually does so that he could not be identified.
Only a few, poor-quality photographs of Deif are known to exist, the most recent taken some 20 years ago.
His hiding place is unknown, and he is reported to be a master of disguise who is able to blend seamlessly into the population.
Deif, whose real name is Mohammed Diab al-Masri, was born in 1965 in Gaza's Khan Yunis refugee camp.
He has been involved with Hamas since the 1980s and took part in many of its operations, including the abduction of soldiers and suicide bombings.
He was appointed head of Hamas's military wing in 2002 after the death of his predecessor, Salah Shehade, in a raid.
Two years earlier, at the start of the second intifada, Deif had escaped, or was freed, from a prison run by Yasser Arafat's Palestinian Authority.
Shortly after he was named Hamas's military head, Israel launched its fifth bid to assassinate him in Gaza, in an attack that left him severely wounded, with unconfirmed reports suggesting he had been left paraplegic.
The last time Israel tried to assasinate Deif was in 2014 when it launched an air strike on Gaza, killing his wife and one of the couple's children.
Deif's enemies have dubbed him the "cat with nine lives" while Palestinians consider him a living legend.
Yahya Sinwar, the 'strongman' of Gaza
A former commander of the Hamas military wing, Sinwar, 61, was elected in 2017 as head of militant group in Gaza.
He rose through the ranks of Hamas as a fierce advocate of armed struggle against Israel and is considered by the group as their "defence minister".
An aura of mystery surrounds the slightly-built, Hebrew speaker Sinwar, who knows Israel well, having spent 23 years in Israeli jails before his release in 2011 in a prisoner exchange involving French-Israeli soldier Gilad Shalit who was held captive by Hamas.
On Thursday, Israeli army spokesman Richard Hecht told reporters the offensive on Gaza targets senior Hamas leaders including Sinwar.
