"The situation between us and Hamas is one of an inevitable clash. It's only a question of 'when' not 'if,'" Olmert said during a visit to the headquarters of Israel Defense Forces' (IDF)Gaza Division.

His tour was accompanied by Israeli Defense Minister Ehud Barak, IDF Chief of Staff Gabi Ashkenazi and several top military commanders, according to a press release from the Prime Minister's Office.

"We don't intend to violate the calm, we would like to continue the truce, but we will act in any situation in which a terror attack against IDF soldiers or Israeli civilians needs to be thwarted," Barak said.

"We are looking at this relative calm around and we know that many things are happening beneath the surface," he warned.

Israeli army killed at least six Hamas gunmen and one Islamic Jihad militant during the operation on November 4, which is the first action in Gaza since the Egypt-brokered ceasefire took effect on June 19.

The action was aimed at raiding a tunnel dug by Hamas near the Israeli border which the army claimed to be used in an imminent kidnapping attempt, IDF spokesperson said.

In response, Palestinian militants in Gaza fired over 60 Qassam rockets and mortar shells in the following days.