Gaza's civil defense agency said 21 people were killed and dozens more wounded in multiple Israeli air strikes on Saturday.
Saturday was one of the deadliest days since the U.S.-brokered truce between Israel and Hamas came into effect on Oct. 10, after two years of war.
The Israeli military claimed an "armed terrorist" had crossed the so-called Yellow Line within the Gaza Strip, behind which Israeli forces have withdrawn, and fired at Israeli soldiers.
Mahmud Bassal, spokesman for the civil defense agency, told AFP there were "21 martyrs this evening in five separate Israeli air strikes, in a clear violation of the cease-fire in Gaza."
They included seven killed and more than 16 injured in a strike on a house in Nuseirat in the central Gaza Strip, and four killed and several injured in an air strike on a residential apartment in the Al-Nasr district, west of Gaza City, he said.
According to the health ministry in Gaza, as of Thursday, 312 Palestinians had been killed by Israeli fire since the truce took hold.
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