By Agence France-Presse
The clamp down on "illegally published books" also comes as the Vatican and Beijing negotiate a historic agreement on the appointment of bishops in China.
"Bibles and books without publication numbers have all been removed in recent days," a merchant on Chinese e-commerce platform Taobao told AFP, without giving details on how authorities have enforced the ban.
However, another merchant said she can list Old Testament editions of the Bible while English editions were still available in search results on Amazon China and Dangdang.com.
Online sales of other major religious texts including the Koran and the Taoist Daodejing did not appear to be affected.
All books sold in China technically must go through an official approval process, but Bibles have been readily available in recent years.
The General Administration of Press and Publication (GAPP) governs the distribution of China's equivalent of the International Standard Book Number (ISBN), which is needed for books to be legally sold in the country.
China's State Council and GAPP authorities did not immediately respond to AFP's requests for clarification.
Jin Mingri, pastor of the Protestant Zion Church in Beijing, which is not registered with the government, said the restrictions were tied to "overall tightening in the overall environment."
"Maybe (authorities) think that the spread of the Bible on informal channels is not conducive to state ideology," Jin told AFP.
"This certainly has an impact on believers' access to the Bible," he added.
The state-linked China Christian Council estimates the country has around 20 million Christians -- excluding Catholics -- in official churches supervised by the authorities.
But the true number of worshippers could be higher, at least 40 million to 60 million, according to some estimates, as some pray at "underground" or "house" churches which seek to exist outside government control.
Meanwhile China's roughly 12 million Catholics are divided between a government-run association, whose clergy are chosen by the atheist Communist Party, and an unofficial underground church loyal to the Vatican.
The Vatican relaunched long-stalled negotiations on the appointment of bishops with Beijing three years ago.
China's officially atheist government is wary of any organised movements outside its own control, including religious ones, and analysts say controls over such groups have tightened under President Xi Jinping.
The national security law explicitly bans "cult organisations", which includes Falun Gong, Buddhist-inspired groups and several Christian groups.
A new regulation in Xinjiang bans religious activities in schools and stipulates that parents or guardians who "organise, lure, or force minors into religious activities" may be reported to the police.
The far-western region is the homeland of the Uighurs -- a traditionally Muslim group, many of whom complain of cultural and religious repression and discrimination.