An explosion ripped through a car east of Gaza City late Thursday, witnesses said, and hospital officials said one person was killed and another was seriously wounded. Hamas security officials said Israel fired a surface-to-surface missile at a group of Hamas fighters, killing one and wounding an unspecified number of other fighters, including one who was seriously hurt. The Israeli army, which customarily acknowledges its air and ground operations against Palestinian militants, denied involvement in its initial response. Some blasts that do not involve the military are caused by explosive devices intended for use against Israel that go off prematurely. In related news, a Palestinian rocket hit a house late Thursday in the southern Israeli city of Sderot, a frequent target of militant attacks. No injuries were reported. In all, seven rockets were fired throughout the day at Israel from Gaza, including at least three that landed in Israeli territory.