Hamas and other Palestinian groups in the Gaza Strip have a variety of home-made or smuggled rockets at their disposal to use against Israel. Following are some facts about the rocket arsenals and the threat they pose:
* Each militant group in Gaza has a different name for the rockets they build themselves: Hamas's are Qassams, Islamic Jihad calls them al-Quds, using the Arabic name for Jerusalem, and Fatah's armed wing calls them al-Aqsa, the name of the main mosque in Jerusalem. However, Qassam, named after a Palestinian guerrilla leader of the 1930s, has become the common term.
* Many shorter-range rockets -- those that are fired toward the Israeli town of Sderot, just across the border from Gaza -- are home-built, with metal fins welded onto a 1.5-meter (5-foot) length of 15-cm (six-inch) pipe that is packed with explosives. Hamas is estimated to have several thousand of such rockets.
* The first Qassams were developed and fired in 2001 and had a range of about 4 km (2.5 miles). Since then, various upgrades have been developed -- dubbed Qassam-2, Qassam-3, etc -- which have taken the effective range up to about 15 km.
* Since 2001, Hamas and other groups have fired about 4,100 rockets and a similar number of mortar rounds into Israel, the Israeli Foreign Ministry says. Over 1,500 rockets were fired in 2008. Such fire killed 16 civilians and 2 soldiers between 2001 and late 2008. A further 3 civilians and a soldier have been killed by rockets since Israel launched an offensive on December 27.
* Militants have also smuggled in through tunnels from Egypt longer-range, factory-built rockets, mostly Soviet-designed 122-mm missiles generically called Katyushas. Derived from the "Stalin's Organ" multiple rocket systems of World War Two, these are similar to those used on Israel in 2006 by Lebanon's Hezbollah, like Hamas an ally of Iran and Syria.
* Katyusha is a Russian diminutive of Catherine. More recent versions, which Hamas fires singly in an improvised way rather than from the truck-based multiple launchers used by regular armies, are commonly known as Grad -- Russian for "hailstorm." Hamas's ally Iran is among countries that make such missiles.
* Depending on the version, these have ranges from 20 km to over 40 km, putting Israeli cities like Ashdod, Ashkelon and Beersheba within range. Hamas and Israel say the group has even longer range rockets. The Jewish state's metropolis Tel Aviv lies 60 km north of Gaza.
* As well as the ground-to-ground rockets, which have a limited accuracy, militants are also said to have a limited number of shoulder-fired ground-to-air missiles that could be used against helicopters or slow-moving planes, although there is no evidence that they have been used.