The latest incident comes as the East Asian monsoon continues to unleash atmospheric chaos across the world's second-largest economy.
The banks of a river running through the grasslands of Inner Mongolia burst late on Saturday, washing away 13 campers on the outskirts of the city of Bayannur, a major agricultural hub.
One person was rescued with two unaccounted for.
A search and rescue operation involving more than 700 people was underway, according to state news agency Xinhua.
China has suffered weeks of extreme weather since July, battered by heavier-than-usual downpours with the monsoon stalling over its north and south.
Weather experts link the shifting pattern to climate change, testing officials as flash floods displace thousands and threaten billions of dollars in economic losses.
Bayannur is an important national grain and oil production base, as well as a sheep breeding and processing centre.
At the other end of the country, a three-and-a-half-month fishing suspension in the southern province of Hainan ended on Saturday after agricultural affairs officials ordered ships to shelter in port owing to persistent, heavy rain.
In the southwestern province of Sichuan, severe weather on Friday killed two people and injured three others at a beer festival in the city of Mianzhu, after a truss fell on them, according to a local police report.
The deluge in Inner Mongolia follows a deadly downpour in Beijing - just under 1000 km away - late last month which killed at least 44 people and forced the evacuation of more than 70,000 residents.
The central government announced fresh funding for disaster relief, taking the total allocated since April to at least 5.8 billion yuan.
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