GAZA, Palestinian Territory – Israel’s military fired on Hamas installations in Gaza after a rocket launched from the territory exploded inside Israel on Monday, with no reports of casualties on either side.

Hamas, the Islamic militant group that rules Gaza, has largely adhered to a cease-fire that ended a 50-day war with Israel in 2014, but other militant groups occasionally fire rockets or mortar rounds over the frontier. Israel holds Hamas responsible for all incoming fire.

Sirens wailed in parts of southern Israel warning of incoming rockets early Monday. The military said one exploded in an open field. Soon after the attack, it said a tank fired at a Hamas position near the frontier.

The uptick in violence continued throughout the day. Gaza residents, who asked not to be identified for security reasons, said Israeli airstrikes targeted three Hamas-run militant training sites. The military confirmed those as well as a series of additional airstrikes during the evening, saying they were in response to the rocket and to shots fired at troops operating near the frontier.

Israeli military spokesman Lt. Col. Peter Lerner said the military “will not tolerate rocket fire toward civilians and will continue to ensure security and stability in the region.”

Hamas spokesman Hazem Qassem blamed Israel for the escalation.

There was no immediate claim of responsibility in Gaza for the rocket attack. Jihadists who support the Islamic State group have taken responsibility for similar attacks in the past.