Three Palestinian brothers were killed early Tuesday in an Israeli airstrike at smuggling tunnels in southern Gaza Strip town of Rafah, witnesses and medical sources said.

The latest incident intensified violence that flared up in the Gaza Strip suddenly, ending months of quietness between Palestinians and Israeli army and opening the door for possible escalation.

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

The witnesses said more workers have gone missing in the sudden raid, and hundreds of people and rescue workers gathered in the area to dig out the dead bodies and the missing workers.

The tunnels are used to bring in a wide array of products that are no longer allowed through official crossing points due to an Israeli blockade that has been in place for more than two years.

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.

Tensions entered the 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.

Abu Mujahed, a spokesman for the Popular Resistance Committees (PRC), a Palestinian militant group, said that the firing of mortars was in response to the death of the 20-year-old farmer.

"There is an understanding between all factions, including Hamas, to respond to the Israeli violations," he told reporters in Gaza.

Meanwhile, Hamas spokesman Ismail Radwan said that "Israel is the only one to blame for the escalation."

In a statement sent to the media, he accused Israel of "working to increase military tension in Gaza in preparation for a new round of confrontation."

Since Israel ended its 22-day major military offensive in Gaza in 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 26, 2009)