Israel-Palestine conflict: what is the Islamic Jihad - and who were the leaders killed in Gaza air strikes?

Islamic militant groups are already threatening violent reprisal against Israel, after it carried out a series of targeted air strikes in the Gaza Strip - killing three senior commanders of the Islamic Jihad.

The air strikes - which took place overnight Monday through to Tuesday (9 May) - pummelled densely populated areas, hitting the top floor of an apartment building, a house in Gaza City, and a third house in the southern town of Rafah.

The Palestinian Health Ministry said at least 12 civilians had been killed and an estimated 20 people were wounded, some in serious or critical condition.

Israel's said it targeted several militant training sites as well before the air strikes halted at daybreak. After a lull, the Israeli military said warplanes struck militants carrying anti-tank guided missiles in the enclave’s southern city of Khan Younis later on Tuesday.

The military has said it was targeting commanders in the Islamic Jihad. But what exactly is the Islamic Jihad, and who were the men killed?

What is the Islamic Jihad?

The Islamic Jihad is one of two Iranian-backed groups that oppose the existence of Israel and its occupation of the area, and possess large arsenals of rockets and other weapons.

While Hamas functionally controls the Gaza strip, Islamic Jihad has been a constant presence in the Gaza and West Bank conflict zones since at least the 1980s.

Operations of its militant wing - also known as the Saraya - have controversially included suicide bombings and attacks on Israeli civilians, as well as firing rockets into Israel.

In recent years, the larger and more powerful Hamas has stuck to the side-lines, allowing Islamic Jihad to carry out attacks. Islamic Jihad reportedly has closer ties to Iran - which is known to fund both organisations. Israel, the United Kingdom, the European Union, and the United States all classify both groups as terrorist organisations.

The groups have already made threats of retribution for the deaths. Dawood Shahab, an Islamic Jihad official, said there would be a “unified Palestinian response” to the strikes at a time and place of its choosing, while Hamas leader Ismail Haniyeh - who lives in exile - warned that Israel will “pay the price” for the killings, adding: “Assassinating the leaders with a treacherous operation will not bring security to the occupier, but rather more resistance.”

Why are Israeli forces targeting the group?

Islamic Jihad bombarded Israel with dozens of rockets last week after one of its members in the West Bank died from a hunger strike, while in Israeli custody.

The New York Times reports the Israeli military confirmed on Tuesday that it had targeted and killed the three Islamic Jihad leaders, as they were responsible for rocket attacks against Israel and other attacks against Israeli citizens in the occupied West Bank.

The roots of the Israeli-Palestinian conflict go back 100 years, when Britain created a homeland for Jewish people on land which already had an Arabic-speaking populace. Violent conflict and outright war have been raging ever since, but tensions have been steadily rising since Israeli Prime Minister Benjamin Netanyahu’s new far-right government took office late last year.

The government is dominated by religious and ultranationalist hard-liners, who have ramped up controversial activities like demolishing family homes of convicted terrorists.

Israeli police also recently attracted criticism for storming a mosque in a site important to both the Jewish and Muslim faiths, on some of the holiest days of the year, with the situation devolving into airstrikes.

Who were the senior leaders killed in the airstrikes?

The commanders have been identified as Khalil Bahtini, the Islamic Jihad commander for the northern Gaza Strip; Tareq Izzeldeen, the group’s intermediary between its Gaza and West Bank members; and Jehad Ghanam, the secretary of the Islamic Jihad’s military council.

At least 12 civilians were also killed in the attacks, which has drawn condemnation from Palestinians and the international human rights community.

In a statement, the Islamic Jihad said the wives of the three commanders were among the dead, although witnesses and family members have said only two of their wives were killed. The Palestinian Health Ministry said the dead included four women and four children.

The Russian diplomatic delegation in the West Bank, said one victim - called Jamal Khaswan - was a Russian national, and that his wife and son were also killed. Mr Khaswan was a dentist who lived downstairs from Izzeldeen in Gaza City, they said.

Tor Wennesland, the United Nation's envoy to the Middle East, said he was “deeply alarmed” and condemned the civilian deaths, calling on all sides “to exercise maximum restraint” in the days to come.