Meetings between Hamas leaders and U.S. hostage negotiator Adam Boehler in recent days have focused on the release of an American-Israeli dual national being held by the militant group in Gaza, a senior Hamas official told Reuters on Sunday.

Israel carried out an air strike on militants in northern Gaza on Sunday, rattling an already fragile ceasefire as it prepared for fresh talks in Doha on the future of its truce with Hamas.

Israel estimates that 59 hostages are still held in Gaza with at least 22 of them alive. They are expected to be set free in a second phase of the Gaza ceasefire and prisoner exchange agreement, which would require Israel to fully withdraw its forces from Gaza and end the war permanently.