Gaza City, Nov 24 (DPA) Israeli warplanes bombed three targets in the Gaza Strip before dawn Tuesday, responding to two rockets fired into southern Israel the previous evening, the Israeli military and Palestinian health officials said.

Two smuggling tunnels in Rafah, on the border with Egypt, and a metal workshop in an outlying Gaza City area were destroyed, said witnesses.

Three Palestinian civilians were moderately injured in the attacks in Rafah, reported the Abu Yousef al-Najar hospital. No casualties were reported in the Gaza City strike.

An Israeli military spokesman in Tel Aviv said Israel was not behind an earlier explosion reported elsewhere in eastern Gaza City, shortly before midnight.

Two Palestinian militants of the Qassam Brigades, the armed wing of the radical Islamist Hamas movement ruling the Gaza Strip, were killed in the blast, heard throughout Gaza City.

Hamas was mum on the cause of the explosion, but other sources close to it said the two fatalities, identified as Mohammed al-Nawati and Ahmad Abu Ghanima, were known for their involvement in producing weapons for Hamas.

The sources said the two were likely killed in a 'work accident' - a local euphemism for the accidental or premature explosion of a bomb or rocket as it is being handled by militants.

The Israeli army spokesman said that, since last winter's Gaza offensive, Palestinian militants had fired some 270 rockets and mortar shells at Israel from Gaza, compared to more than 3,300 in the previous year in the lead-up to the war.

'That is a huge difference and very important for us to emphasize,' the spokesman told DPA.

Some 1,400 Palestinians were killed in the three-week, Dec 27, 2008 - Jan 18, 2009 offensive, most of them civilians, according to human rights groups. The Israeli shelling and ground campaign against Hamas targets in the densely-populated strip also caused widespread destruction.

Israel said it launched the offensive in a bid to curb near-daily rocket and mortar shells from the area at its southern towns and villages. Since the offensive, the sides have largely abided by an unspoken truce, with Israel responding with lone airstrikes to sporadic ongoing rocket and mortar attacks.

The latest rockets and airstrikes come amid reports of progress in German-mediated indirect negotiations on a prisoner exchange between Israel and Hamas.