JERUSALEM — Thousands of Gaza residents on Monday attended funerals of three Palestinian boys killed by an Israeli airstrike along the security fence with Israel the day before.

The Israeli military said three figures had been spotted trying to sabotage the security fence and had appeared to be laying an explosive device under the cover of darkness.

Gaza’s militant factions accused Israel of killing the boys “in cold blood” and said claims they had been planting a bomb were fabricated.

In the light of day Monday, there appeared to be no evidence of an explosive device in the area. But there were suggestions in Israel that the boys might have been sent by militants as scouts, to test whether the area was under military surveillance or to cut a hole in the fence for others to go through later.