A Palestinian man, believed to be a member of Hamas -- an Islamist group that controls the Gaza Strip -- was killed during shelling by the Israeli army on Wednesday, according to media reports. The Israeli military claimed that it had returned fire after its routine patrol on the Israeli side of the border came under attack from snipers in southern Gaza.

“Following the sniper attack on the Gaza border, IDF (Israel Defense Forces) and ground forces responded immediately to the threat,” the Israeli military said, in a tweet, on its official Twitter account. The army also described the attack as the “gravest” incident since the conclusion of the war in Gaza in August -- a sentiment that was echoed by Hamas, according to media reports.

“This is a grave escalation … The occupation is fully responsible to all of the consequences of the escalation. The resistance has a right to defend itself and its people,” a Hamas spokesperson said, according to a report by The Jerusalem Post.

The dead man was reportedly identified as Tayseer Asmairi. The 33-year-old is a member of the al Qassam Brigades, which is Hamas’ armed wing.

The latest flare-up comes just days after the Israeli military carried out airstrikes on a Hamas facility in the Khan Younis area of southern Gaza. The incident has the potential to break an uneasy calm that has prevailed in the Palestinian enclave since the end of the most recent war in the region. Over 2,100 Palestinians, including hundreds of children and 72 Israelis, were killed in the 50-day war that also left hundreds of thousands of people homeless in the Gaza Strip.