Israel said it would call up 10,000 reservists as Palestinians vowed to avenge Israel's killing of three Hamas commanders in Gaza.
The strike on Thursday levelled a four-storey house in a densely populated neighbourhood of the southern town of Rafah, killing six people, including Mohammed Abu Shamaleh, Raed al-Attar and Mohammed Barhoum. Both Israel and Hamas identified the commanders killed in the air strike.
Israel said the trio had played a key role in expanding Hamas' military capabilities in recent years, including digging attack tunnels leading to Israel, training fighters and smuggling weapons into Gaza.
Thousands of Palestinians marched through Rafah in a funeral procession firing guns, waving flags of different militant groups and chanting religious slogans. Those killed were carried aloft through the crowd on stretchers, wrapped in green Hamas flags.
Sami Abu Zuhri, a Hamas spokesman, said Israel "will not succeed in breaking the will of our people or weaken the resistance" and "will pay the price".