Palestinians in north Gaza fired at least two mortars towards Sderot Sunday evening, but there were no reports on injury or damage.
Security officials initially believed that the siren heard throughout the Negev region was the result of a malfunction, but later reported that two mortar shells landed near the security fence separating Israel from Hamas-ruled Gaza.
Police forces were combing the area for additional mortar landing sites.
"We clearly heard an explosion, so I don't understand the reports of a possible false alarm," a Sderot resident said.
Saturday night saw Israel Air Force jets bomb a tunnel in the northern Gaza Strip. The Israel Defense Forces Spokesperson's Office said the tunnel was dug inside a building located about 1.5 kilometers (less than 1 mile) from the border fence, and was aimed at allowing terrorists to infiltrate Israel and carry out an attack against civilians or soldiers.
The IDF said the strike was a joint activity with the Shin Bet and that an accurate hit had been identified. A military official added that the attack was a response to the firing of a Qassam rocket from the northern Gaza Strip on Saturday morning.
The rocket landed in an open area near a community in the Sdot Negev Regional Council at around 6 am. There were no reports of injuries or damage.
Last Tuesday, three Palestinians were reportedly killed as the IDF attacked a weapon smuggling tunnel in the Rafah area. The strike was a response to a firing incident near the border fence, which left one Palestinian killed and an IDF soldier lightly injured.
The day before Palestinians fired a mortar shell at an IDF force, which hit group of teenagers near the Gaza Strip town of Beit Lahiya, reportedly killing a 15-year-old boy. The Israeli army reported that the Palestinians had approached the fence and did not obey calls to stop.