OCCUPIED JERUSALEM: The Israeli air force bombed the Gaza Strip early Sunday for the second time in three days after new rocket fire from the territory hit southern Israel, the military said.

Aircraft hit "terrorist infrastructure" in the north of Gaza, a military statement said, without elaborating.

The government also ordered the closure of the Erez and Kerem Salom border crossings until further notice.

The rocket hit open ground south of the port of Ashkelon, which was also the target of three rockets fired on Wednesday night.

The army said there no casualties.

On Friday evening, the military deployed batteries of its Iron Dome air defence system around Ashkelon as a precaution, Israeli media reported.

Rocket fire from Gaza on May 26 also drew Israeli air raids.

Nobody was hurt on either side in any of the exchanges.

Israeli media have said the latest round of rocket fire could be related to infighting between Gaza's Hamas rulers and its hardline Islamist opponents.

On Tuesday, Hamas security forces shot dead a Salafist leader in Gaza City during a confrontation as Hamas stepped up measures against Islamic extremist groups.

Since last summer, when Israel and Hamas fought a war in and around Gaza, there have been growing signs of internal unrest between Hamas security forces and extremist splinter groups.

Salafists are Sunni Muslims who promote a strict lifestyle based on that of early "pious ancestors". In Gaza, they have made no secret of their disdain for Hamas over its observance of a tacit ceasefire with Israel and its failure to implement Islamic law.