A Cardiff museum had to close its front doors after demonstrators chanting "Free Palestine" entered the building.
Protesters went into National Museum Wales in the city centre, where they displayed Palestinian flags.
Saturday saw a pro-Palestinian march in Cardiff city centre for the fifth weekend in a row over the Gaza war.
The museum apologised for any inconvenience, but said it shut the doors to protect the safety of visitors and staff.
It said people could still access the museum via the Reardon Smith Theatre on the side of the building, and they would open the front doors as soon as it was safe to do so.
Israel launched a major military campaign in the Gaza Strip to destroy Hamas, which it considers a terrorist group, in retaliation for the 7 October cross-border attack by hundreds of gunmen.
At least 1,200 people were killed in Hamas's assault on Israel and about 240 others were taken hostage.
Since Israel started its counterattack, Gaza's Hamas-run health ministry has said 11,400 people have been killed in the territory and the United Nations has warned of a "humanitarian disaster".