Lebanon saw its deadliest day of fighting in months, heaping pressure on stalled U.S.-Iran negotiations while Washington preps fresh sanctions.

The Israel Defense Forces said on Sunday that it killed Abu Hassan Alaa, a senior Hezbollah commander, in southern Lebanon a day earlier. A total of 11 people died in the Israeli strikes, making them the deadliest since the sides agreed to a ceasefire at the beginning of June.

Israeli Prime Minister Benjamin Netanyahu said the strikes were in retaliation for a Hezbollah attack injuring three soldiers on Saturday. Israel said on Sunday it would strike the Iranian proxy group again if threatened.