Updated

JERUSALEM (AP) — Israel's military says it mistakenly killed three Palestinian civilians, including a 91-year-old man, in northern Gaza this week.

Relatives and a Palestinian rights group say the elderly farmer, his 16-year-old grandson and another 17-year-old relative were hit by Israeli fire as they grazed sheep close to the Israeli border Sunday.

Israeli Brig. Gen. Eyal Eisenberg said Wednesday that forces opened fire after spotting a Palestinian pick up a rocket off the ground and point it at soldiers. Eisenberg says investigators determined they weren't combatants, and apparently had found a stray weapon left behind by militants.

Israeli troops and Palestinian rocket squads often clash along the border. But many Palestinian farmers till land there. A rights group says 13 civilians have been killed this year.