The quake struck at 8.49am (0049 GMT) and is the biggest in the region for more than 50 years.
The epicenter was near the city of Jiujiang, home to half a million people and a popular tourist destination.
"Six people were killed in Jiujiang county," a local official earlier said. "Another 247 were injured, and 8,072 buildings were toppled."
An official in nearby Ruichang city said five people had been killed there, while 39 were injured.
One fatality was recorded near the city of Wuxue, in neighbouring Hubei province, an official there said.
"We'd just finished our breakfast, when we heard a huge roar," said a civil affairs official from Ruichang named Liu, "then the houses started shaking, and we just jumped outside,"
"The earthquake this morning was quite scary," said a shopkeeper in Ruichang who would only give her surname as Zhou.
Milder trembling that she assumed was an aftershock was felt again around 1pm (0500 GMT), Zhou said.
|Jiangxi is a popular tourist |
Many people in Ruichang, which has a population of about 420,000 people, were staying outside for fear of more aftershocks.
"Basically, everyone in Ruichang is right now out huddling in
the street," said Liu, the civil affairs official. "I guess by night
fall we may need tents and blankets for them."
Tents were set up outside the local hospital, she said.
Temperatures in the region were relatively mild, hovering around 10 degrees Celsius, weather reports said.In Beijing, the civil affairs ministry was preparing to send emergency relief supplies to the affected region, according to the Xinhua news agency.