Israel launches fresh strikes on besieged Gaza Strip

Israel hit Islamist militant sites in Gaza with air strikes on Friday in retaliation for incendiary balloon launches from the Palestinian enclave, in the latest unrest since a ceasefire ended May's conflict.

Security sources with Hamas, the Islamist group that runs Israeli-blockaded Gaza, said the strikes hit training sites. There were no injuries reported. 

A statement from Israel's army said: "In response to the arson balloons fired towards Israeli territory today, (military) fighter jets struck... a weapons manufacturing site belonging to the Hamas terror organisation."

On Thursday, Israel's fire service said that incendiary balloon launches from Gaza had sparked four minor fires in the southern Eshkol region, on the Gaza border. 

The blazes were "small and not dangerous" and were quickly brought under control, a statement from the fire service said.  

Read also: Shin Bet informants 'leading serious violence in Palestinian communities', senior Israeli police officer says

"A fire investigator... determined that all the fires were caused by incendiary balloons (from Gaza)", the statement said. 

Eleven days of deadly fighting between Israel and Gaza's Hamas Islamist rulers, as well as other Palestinian armed groups based in the enclave, ended on May 21 with a ceasefire declaration. 

There was no immediate indication as to which Gaza-based group was responsible for the balloon launch. 

There have been multiple flare-ups since the ceasefire, including a series of balloon launches last month as well as Israeli air strikes on the besieged Strip. 

Following an exchange of fire on June 18, Israeli army chief ordered forces to be ready "for a variety of scenarios including a resumption of hostilities".

The deadly bombardment in May killed 260 Palestinians including at least 66 children, according to Gaza authorities. Residential and commercial buildings, including those housing internationally news organisation such as The Associated Press and Al Jazeera, were completely decimated.

In Israel, 13 people were killed, including a soldier, by rockets fired from Gaza, the police and army said.

Israel has maintained a crippling blockade on Gaza since 2007, the year Hamas took power, which the Jewish state says is necessary to contain armed groups in the enclave.

Agencies contributed to this report.