Gaza's Hamas-run civil defence says 11 people were killed, all from the same family, after the bus they were in was hit by an Israeli tank shell in northern Gaza.
The Abu Shaaban family, it said, were trying to reach their home to inspect it when the incident happened in the Zeitoun neighbourhood of Gaza City on Friday night.
This is the deadliest single incident involving Israeli soldiers in Gaza since the start of the ceasefire eight days ago.
The Israeli military said soldiers had fired at a "suspicious vehicle" that had crossed the so-called yellow line demarcating the area still occupied by Israeli forces in Gaza.
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Israeli soldiers continue to operate in more than half of the Gaza Strip, under the terms of the first phase of the ceasefire agreement.
Civil defence spokesman Mahmud Bassal told AFP news agency the victims were killed while "trying to check on their home" in the area.
The dead included women and children, according to the civil defence.