At least 20 Palestinians, including 9 children, have been killed by a series of Israeli air strikes across the Gaza Strip on Monday evening, according to the latest reports from Palestinian health ministry.

Eyewitnesses said the strikes hit crowded neighbourhoods, killing numerous civilians. Two of them were children from the al-Masri family in Beit Hanoun:Ibrahim, 11, and Marwan, 7.

"My children were martyred. I cannot find any justification whatsoever for targeting someone passing through overcrowded civilian neighbourhoods where dozens of children usually play," said their father, Youssef al-Masri.

'It was a nightmare': Israeli air strikes kill 20 in Gaza