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The Popular Front for the Liberation of Palestine (PFLP) has said three of its fighters were killed in Israeli strikes on Beirut on Monday morning.
Established in 1967, the armed group is part of the Palestinian Liberation Organisation (PLO), a rival to the ruling Fatah party in Gaza and an opposer to the two-state solution.
History
An offshoot of the Arab Nationalist Movement, the PFLP was founded after the 1967 war by Palestinian Greek-Orthodox Christian George Habash.
After graduating from the school of medicine at the American University of Beirut, Dr Habash returned to his home in the occupied city of Lod, also known as Lydda, in the 1967 war, which was raided by Israeli forces, causing large civilian displacement, seeking food, water and shelter in what became to be known as the "Lydda death march".
A year later, he left for Amman, setting up a free clinic for refugees, but was also heavily involved in organising political movements against the West and Arab states.
He stepped down from his position at the PLFP in 2000 and died eight years later of a heart attack at the age of 81 in Jordan. Palestinian President Mahmoud Abbas declared three days of mourning and Hamas extended its condolences.
Vision and attacks
The PFLP believes Israel should not exist and advocates a single democratic and secular state of Palestine.
A year after its founding, the PFLP splintered, with the PLFP-General Command forming in opposition to the Marxist origins of the group and being designated a terrorist organisation by the US, UK and Israel.
In Jordan, Dr Habash was convicted of being involved in a coup and was sentenced in absentia to 33 years.
In 1970, the PFLP hijacked four passenger planes headed to New York City and London, three of which were forced to land at Dawson's Field in Jordan.
PFLP fighters took passengers hostage and blew the planes up on the tarmac. Dr Habash is accused of masterminding these attacks, which preceded the 'Black September' crackdown by Jordan's King Hussein on the PLO.
In 1972, Dr Habash said the group would stop hijacking planes as such acts were at odds with its "Arab and international alliances". In the same year, the PLFP killed 27 people at an airport in Lod.
Dr Habash remained opposed a two-state solution to the Israel-Palestine conflict, even after the Oslo Accords were signed in 1993.