BEIJING—Seven people at a military hospital in northeastern China were killed on Thursday in a knife attack, local authorities and state media said, following a spate of violent assaults on medical workers nationwide.

The predawn incident in Beidaihe—a resort town favored by China’s Communist Party elite—left six nurses and an administrator dead and one other person injured, local authorities said in a statement published on a verified Weibo social-media account. The official Xinhua News Agency said the attacker used a knife.

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