Gaza City: Here is a list of the main armed groups in the Gaza Strip.

- The Islamist Hamas movement, which has ruled Gaza since 2007, has a force of 20,000 fighters, according to the International Institute for Strategic Studies. Around half belong to its armed wing, the Ezz Al Deen Al Qassam Brigades. Additionally, more than 10,000 belong to Gaza’s security forces and its Hamas-founded Executive Force.

The IISS says the Brigades would bear the brunt of any engagement with Israel, just as during the 22-day Operation Cast Lead over New Year 2009. Their weapons, smuggled into the territory or home-made, include mines, rockets, mortars and light arms.

According to their website, the Brigades first appeared in 1991 during the first Intifada, or uprising.

Over the past five days, the group claims to have fired several rockets at Tel Aviv and one at occupied Jerusalem, which lies some 65km away.

- Islamic Jihad, Hamas’ smaller rival, has a force of about 8,000 men grouped into its armed wing, the Al Quds Brigades. It said on Thursday it had fired an Iranian-made Fajr 5 rocket at Tel Aviv. Created in 1980, it was the first Palestinian Islamist group to engage in armed struggle.

- The armed wing of the Popular Resistance Committees, which was founded in September 2000, is called the Al Nasser Salah Al Deen Brigades. Set up by security elements from Fatah — the political movement currently led by Palestinian president Mahmoud Abbas — its numbers are boosted by defectors from Islamist groups.

In June 2006, the PRC worked with the Ezz Al Deen Al Qassam Brigades and the Army of Islam to kidnap Israeli soldier Gilad Shalit, who was freed in October 2011 in a prisoner swap with Israel in exchange for 1,027 detained Palestinians.

- Salafist jihadists who accuse Hamas of weakness against Israel and in the application of Islamic law. The best known group is the Army of Islam, connected to the powerful Doghmush clan. Aside from the Shalit kidnapping, the group in 2007 snatched BBC journalist Alan Johnston, who was freed by Hamas nearly four months later.

- Armed groups from the Palestine Liberation Organisation (PLO) remain, though they have become less visible since Fatah forces were pushed out of Gaza by Hamas in 2007. Among them are the Al Aqsa Martyrs Brigades and the Abu Ali Mustafa Brigades, the military wing of the Popular Front for the Liberation of Palestine.