China's propaganda authorities have issued an order barring domestic media outlets from doing original reporting on North Korean nuclear and missile issues, sources with knowledge of the situation said Sunday.

The gag order is apparently aimed at preventing the already high tensions over North Korea from escalating before and during the Chinese Communist Party's twice-a-decade congress due to open Wednesday.

After North Korea conducted its sixth and most powerful nuclear test on Sept. 3, Chinese media executives were told that news stories on North Korea must be basically in line with those of the country's official media, according to the sources who spoke on condition of anonymity.