(IsraelNN.com) IDF tanks rolled back into Gaza along with foot soldiers Tuesday afternoon following an early morning roadside bomb explosion and a rocket-propelled grenade attack that killed one soldier and wounded three others, one seriously.

Hamas warned that it has not agreed to a "calm" and that its previous ceasefire announcement is dependent on Israel's re-opening Gaza crossings to all commercial traffic.

"This is a serious attack," Defense Minister Ehud Barak told soldiers during a visit near a base close to the scene of the attack and at the same time it occurred. "We cannot accept it and we will retaliate. I do not think there is any point in saying how."

He carried out his threat within hours as troops reached Khan Yunis in central Gaza. Local residents reported tank fire and Israel Air Force jets over the area. Arab sources also reported that the Air Force struck a terrorist target on a motorcycle, killing or wounding two people. The IDF said the cyclist was responsible for the morning attack.

Hamas responded with mortar fire on the Eshkol region, causing no damages or injuries but returning the area to the status quo of the days before the Cast Lead operation against the terrorist infrastructure in Gaza.

The attack on the IDF patrol occurred around 8 a.m., after two or three terrorists were seen by local Arabs to be planting the roadside explosive that was detonated as an army vehicle passed.

Troops opened fire immediately, and one Arab was killed. His identity was not confirmed, and Gaza sources claimed he was a farmer.
 
The attack came at the same time that United States Middle East envoy George C. Mitchell was scheduled to confer with Egyptian officials prior to his arrival in Israel later this week.