JERUSALEM, Feb. 19 (Xinhua) -- The Israeli fighter jets targeted underground infrastructure in the southern Gaza Strip on early Monday, in response to the projectile that was launched into Israeli territory from Gaza Sunday night.

The underground infrastructure belongs to the Hamas, said the Israeli Defense Forces in a statement issued on early Monday. "The IDF will continue to act in order to ensure the security of the civilians of Israel and will do so by all means at its disposal."

Hamas is accountable for this incident and its consequences, as well as everything happening in and from the Gaza Strip, above and below ground, said the Israeli military.

More than ten missiles were fired from Israeli F-16 fighters in the southern Gaza Strip and no casualties was reported, according to sources from the Gaza Strip.

The intense cross-border fighting persisted for a third straight day.

Earlier on last Saturday, an explosive device attached to the fence between Israel and the Gaza Strip detonated, wounding four Israeli soldiers, two of who were wounded seriously.

In retaliation, Israel said its fighter jets attacked "18 terror targets belonging to the Hamas terror organization" overnight last Saturday.

The assault included airstrikes against a tunnel built by Hamas, the Palestinian Islamist group that runs Gaza, in the Zaytun neighborhood in Gaza city; a military compound near Deir el Balah in the central Gaza Strip; and a military compound in the area of Khan Yunis in the southern Strip. Additionally, a tank targeted two observation posts, the military said.?