Israel and Iran launched fresh attacks on each other overnight into Sunday, stoking fears of a wider conflict after Israel expanded its surprise campaign against its main rival with a strike on the world's biggest gas field.

At least 20 Palestinians were killed in Israeli strikes on the Gaza Strip overnight and into Saturday, according to local health officials. The 20-month war with Hamas has raged on even as Israel has opened a new front with heavy strikes on Iran that sparked retaliatory drone and missile attacks.