Israel killed Hamas deputy leader Saleh al-Arouri in a drone strike in Lebanon’s capital Beirut, Lebanese and Palestinian security sources say, raising the potential risk of the conflict in Gaza spreading well beyond the Palestinian enclave, Reuters reports.

Arouri, 57, was the first senior Hamas political leader to be assassinated since Israel launched a shattering air and ground offensive against Gaza’s Hamas rulers almost three months ago after the group’s shock rampage into Israeli towns.

Israel has long accused Arouri of lethal attacks on its citizens, but a Hamas official said he was also “at the heart of negotiations” conducted by Qatar and Egypt over the outcome of the Gaza conflict and the release of Hamas-held Israeli hostages.

Israel neither confirmed nor denied carrying out the killing, but its military spokesperson Rear Admiral Daniel Hagari said Israeli forces were in a high state of readiness and prepared for any scenario.

“The most important thing to say tonight is that we are focused and remain focused on fighting Hamas,” he said when asked by a reporter about the reports of Arouri’s killing.