Israeli warplanes struck the Gaza Strip early Monday morning in response to a rocket fired at southern Israel on Sunday evening.

The Israeli Air Force struck targets near the cities of Khan Younis and Deir al Balah in the south and center of the Gaza Strip, Palestinian sources in the coastal territory said. The IDF said it hit a training facility belonging to Hamas’s armed wing, the Izz al-Din al-Qassam Brigades in the central Gaza Strip in retaliation for the rocket fired at southern Israel.

The IDF said Sunday’s was the third rocket fired at Israel since the beginning of 2016.

There were no immediate reports of injuries or damage.

One rocket was shot from Gaza at southern Israel Sunday evening, landing in an open field.

No injuries or damage were reported, the IDF said in a statement.

Sirens rang out in the Shaar Hanegev region bordering the Palestinian enclave just before 9 p.m., sending people running for shelter.

Area residents reported hearing at least one large boom. The rocket landed in an open field outside of settled areas, according to initial reports.

The army said it was investigating the incident.

There was no immediate claim of responsibility. Though sporadic rocket attacks are often claimed by small Salafi groups, Israel holds Hamas responsible for all strikes and generally responds with a pro-forma strike on Hamas facilities in the Strip.

The attack came less than a day after a rocket was shot from Gaza but failed to make it into Israeli territory.

Tensions with Gaza have escalated since an Israeli airstrike on a Palestinian cell the army said was on its way to plant an explosive device along the border fence.

One man was killed in the strike and three more were injured, according to Hamas, which vowed revenge and claimed the attack came not from an aircraft but from an Israel Navy ship.

In early January, Israel Air Force fighter jets conducted several air raids on Hamas targets in the northern Gaza Strip after at least two rockets fired from the Palestinian enclave landed in open areas near the southern city of Sderot

Recently the Israeli Army has been deploying artillery batteries along the border with Gaza amid fears of an increase in violence on the frontier.