The stampede occurred at lunchtime on Sunday while traditional food was being handed out to people attending an event to commemorate a late religious leader. (Agencies)
The injured were hospitalized, with four in critical condition, the media report said.
Pictures posted online showed a large crowd, most of them men and many wearing white Islamic caps, standing outside the green mosque, apparently after the incident.
Clothes and shoes were scattered on the ground, along with what appeared to be a collapsed section of scaffolding.
An investigation was under way into the cause of the stampede at the mosque in Xiji, around 280 kilometres (174 miles) south of the regional capital Yinchuan.
Ningxia, in northern China, is home to the Chinese-speaking Hui minority, who are mostly Muslim but distinct from the Uighurs of Xinjiang.
According to government statistics, the semi-desert region's six million Hui make up about 36 percent of its population, with Xiji one of the major Hui population centres.
Ningxia, on the upper reaches of the Yellow river, was the scene of a Muslim rebellion in the 19th century but has no recent history of ethnic tensions or other strife between the Hui and China's Han majority.
In contrast, restive Xinjiang, several hundred kilometers to the west, has seen several deadly clashes between Uighurs and security forces in recent months which authorities have blamed on separatist "terrorists".
Xiji is primarily an agricultural county whose main products include wheat, peas and potatoes.
Ningxia is renowned for its wines, some of which have beaten French vintages in blind tastings, and the industry has already attracted the likes of French luxury group LVMH, owner of Dom Perignon champagne among other brands.
The stampede occurred at lunchtime on Sunday while traditional food was being handed out to people attending an event to commemorate a late religious leader.