Four Palestinians were killed early Tuesday in an Israeli air strike at smuggling tunnels in southern Gaza Strip town of Rafah, witnesses and medical sources said.

Three others were injured when the fighter jets dropped two bombs between Rafah and Egypt, targeting the underground tunnels which the casualties were working inside, the sources added.

The witnesses said more workers have gone missing in the sudden raid.

Israeli media quoted army officials as saying that the bombing was in response to Monday mortar attack from the Gaza Strip. An Israeli soldier was lightly injured when three mortars hit southern Israel. No one has claimed responsibility for the attack.

The tensions entered its second day between Israel and the Palestinians in the Hamas-controlled coastal Strip. On Monday, a 20-year-old Palestinian was shot dead when he approached security fence separating Israel and northern Gaza Strip.

Since Israel ended its major military offensive in Gaza last December and January, there has been no official ceasefire. However, Hamas has maintained a sort of quietness and at some point prevented other groups from firing shells at Israeli communities surrounding Gaza.

(Xinhua News Agency August 25, 2009)