Israel strikes Hamas sites in Gaza in first attack since May fighting

Explosions light-up the night sky above buildings in Gaza City as Israeli forces shell the Palestini

* Israeli airstrikes target Hamas armed training camp * Attacks come after fire balloons launched from Gaza * Tensions high after Israeli nationalist march in Jerusalem * Israel, Hamas fought an 11-day conflict in May   Israeli aircraft struck Hamas sites in Gaza on Wednesday after incendiary balloons were launched from the Palestinian enclave in the first such attacks since the end of 11 days of cross-border fighting last month. The overnight airstrikes gave way to calm by morning, and there were no reports of casualties on either side.