Israeli warplanes hit four targets in the Gaza Strip early Saturday without causing casualties, officials said, after militants fired a mortar and rocket into Israel. The airstrikes targeted three smuggling tunnels along the border with Egypt and another site in central Gaza, apparently used to launch rockets, Palestinian officials said. Medics said there were no immediate reports of casualties. Earlier, Palestinians fired a mortar shell and a rocket into Israel, also without causing casualties, the army said. The army had no comment on the raids, but routinely responds to rocket and mortar fire with airstrikes and there has been an escalation in recent days. A total of 23 mortars and four rockets have been launched at Israel from the Hamas-ruled Gaza Strip since Sunday, the army said. One of the rockets struck near a kindergarten in a southern Israeli kibbutz, wounding a teenage girl. On December 18, Israeli warplanes hit central Gaza, killing five militants as they were about to launch a rocket attack, according to the army and witnesses. The Islamist movement Hamas that controls Gaza has observed a de facto truce with Israel since the end of a 22-day offensive by the Jewish state on the strip in January 2009 aimed at halting rocket fire from militants. Attacks have since been considerably reduced, but more than 200 rockets and shells, most of them homemade, have been fired into Israel this year, according to the Israeli military. On Friday a senior Hamas leader, Mahmud Zahar said the Palestinian Islamist movement is still committed to the truce. 'We declare our commitment to respecting the truce between us and the occupier,' Zahar told a gathering in the Gaza town of Khan Yunis. And he called on Israel to reciprocate and 'stop incursions (into Gaza), halt killings of Palestinians and lift the blockade' imposed on the coastal enclave. 