JERUSALEM, March 25 (Reuters) - Israel has brought forward plans to deploy an Iron Dome rocket interceptor system because of increased mortar and rocket fire from the Hamas Islamist ruled Gaza Strip, the Israeli military said on Friday.

Israel developed the system of radar-guided missiles to blow up small to mid-range missiles after a 2006 war with Hezbollah guerrillas in Lebanon when rockets struck its northern towns.

It had postponed deployment of the system, which had been expected in November, because of debate over its high cost, but it said it had reconsidered after barrages of rocket and mortar fire from Gaza this month sparked fears of another possible war.

The Israeli military said in a statement that its chief of staff, Lieutenant-General Benny Ganz has ordered, in accordance with government directives, to deploy the 'Iron Dome' system across southern Israel in the coming days.

The decision to accelerate the deployment of the system was made in light of recent events in southern Israel and according to security assessments, the written statement said.

The Iron Dome system is said to shoot down rockets with ranges of 5 to 70 km (3 to 45 miles). Other systems are being developed to intercept longer range missiles.

The cost of each interceptor firing is estimated to run at between $10,000 and $50,000.

Defense Minister Ehud Barak said on a visit to a southern army base on Friday that it may take months to fully deploy the system, and reiterated Israel's position that it would respond to any further rocket fire from Gaza.

There were no rocket attacks reported on Friday, but 77 have been fired in the past week.

Israel killed five Palestinian militants this week and another four civilians, three of them children, in stepped up aerial bombardments this week which it said was in response to the rocket fire.

Hamas says that its rocket and mortar attacks are in retaliation for Israeli air strikes.

(Writing by Allyn Fisher-Ilan; editing by Elizabeth Piper)