GAZA -- Witnesses and medical sources said a Palestinian boy was killed and two of his companions were injured in an Israeli military strike in the southeast section of the Gaza Strip. According to witnesses, two shells hit an open playground located east of the town of Khan Younis, killing a six-year-old boy and wounding two others. An official at the Abu Yousef al-Najjar hospital said the two children were moderately injured. Violence broke out again on Friday as the truce barely held on Thursday following three days of cross-border shelling. An Israeli fighter plane conducted several air strikes in the Gaza Strip on Friday night and Saturday morning, injuring 20 people. According to the health ministry in Gaza, Israeli started its attacks on Monday and have already killed 13 Palestinians.