The Israeli military rushed a fifth Iron Dome anti-missile battery into service and deployed it in the Tel Aviv area, the army said. ?

Here are some details on the anti-missile batteries, which cost around $50 million apiece:

* Developed by state-owned Rafael Advanced Defence Systems Ltd to counter rocket fire from Lebanon that hit Israeli towns during the 2006 war with Hezbollah, and from Palestinians in the Gaza Strip, where Hamas Islamists took control in 2007.

* Each truck-towed unit fires radar-guided missiles to blow up short-range rockets, notably of the Russian Katyusha type, as well as mortar bombs, in mid-air. It successfully shot down multiple rockets simultaneously for the first time in tests during July 2010. It was first deployed near Gaza in March 2011. Prime Minister Benjamin Netanyahu has said 10 to 15 batteries would be needed to provide full, if not hermetic, cover.

* An army spokeswoman said that in the first three days of the ongoing Israeli offensive against militants in the Gaza Strip, Iron Dome has intercepted at least 222 incoming rockets - a 90 percent success rate.?

* The system uses a variant of the missile detector on warplanes to spot ground-to-ground rocket and mortar launches. A quick calibration lets it determine whether the missile is on course to hit a populated area, and ignore it if it is not. The manufacturer says Iron Dome also works out the safest spot to detonate the incoming missile.

* Iron Dome is billed as providing city-sized coverage against rockets with ranges of between 5 km (3 miles) and 70 km.

* The system's radar was developed in Israel by Elta. The system which calculates the aim of each interceptor is from Israeli software firm mPrest Systems.