Palestinian militants in Gaza fired a barrage of rockets into Israel on Monday as mourners marked the anniversary of the Oct. 7 attack, without disrupting a nearby ceremony.

Hamas also said it attacked Israeli forces in different parts of Gaza. The Israeli military said it launched a wave of artillery and airstrikes overnight and into Monday to thwart what it said was an imminent attack. It said it targeted Hamas launch posts and underground militant infrastructure.

The fighting on the anniversary underscored the militants’ resilience in the face of a devastating Israeli offensive that has killed around 42,000 Palestinians, according to local medical officials. It has also destroyed large areas of Gaza and displaced around 90% of its population.

Hamas-led militants blew holes in Israel’s security fence and stormed into nearby army bases and farming communities in a surprise attack one year ago, killing some 1,200 people, mostly civilians, and abducting another 250. They are still holding around 100 captives inside Gaza, a third of whom are believed to be dead.

Israel is now at war with Hamas in Gaza and its ally Hezbollah in Lebanon. It has also vowed to strike Iran in response to a ballistic missile attack on Israel last week.