By Laila Bassam, Jana Choukeir and Emily Rose BEIRUT/JERUSALEM, June 20 (Reuters) - Israeli strikes in Lebanon killed at least 20 people on Saturday, Lebanon's state news agency NNA said, one day after a ceasefire with Hezbollah took effect, aimed at halting months of escalating violence. Israel said the strikes were a response to projectiles fired overnight by the Iran-backed group. An Israeli military official said Hezbollah launched more than 50 projectiles at Israeli forces in southern Lebanon, prompting attacks on what the official described as "Hezbollah targets".