Police in Xinjiang have refused to issue travel documents to Uyghurs seeking to visit Saudi Arabia for the pilgrimage, Dilxat Raxit, spokesman for the World Uyghur Congress said in a statement.
Travel documents were also being refused to Uyghurs applying to go abroad to visit relatives and friends, he said.
Local governments in Xinjiang were further "educating" religious followers on China's religious policy in a video entitled "The Propaganda Plan on the Pilgrimage Policy", the statement said.
Pilgrims who are approved to go, need to obtain the necessary paperwork from their local county and township government offices, as well as from religious authorities.
"We strongly condemn the Chinese government, which has thoroughly restricted Uyghur Muslims from going to worship in Makka or attending other legitimate overseas religious activities," Raxit said.
In recent days up to 43 Muslim pilgrims have been detained in Artux and Akto, cities near Kashgar, after preparing for pilgrimages, the group said.
Police in Akto city said they had heard of up to 31 people being detained at a local border crossing, but were unaware of the details.
"This incident didn't happen in Akto, it occurred at a border crossing near here. The police from Kashgar are aware of what happened," an officer named Duan said.
Kashgar police refused immediate comment.
An official at the Xinjiang Religious Affairs Bureau in the regional capital Urumqi said the only requirements for pilgrims was that they needed to be in good health, mentally fit and have the economic funds for the trip.
Uyghurs reportedly are facing
restrictions on overseas travel
"As for the police, I don't know what requirements they have," the official said.
Muslim separatists in Xinjiang have long called for the re-establishment of an independent area in the region called East Turkestan.
Xinjiang, a strategically important region bordering Central Asia, is home to a number of ethnic groups, of which the Turkic-speaking Uyghurs form the majority.
Raxit also said China was capitalising on the global anti-terrorism campaign to crack down on ethnic Uyghurs and others in its north-western Xinjiang region.
"We have the right to express our political views. Look at Canada's Quebec. They have people calling for independence, but the government there doesn't call them terrorists," he said.
Global anti-terror facade
Human rights groups have accused the Chinese government of using the global anti-terror campaign to harshly punish Uighurs who hold dissenting views, even those who were non-violent.
China alleges the groups have plotted or carried out bombings, killings and other violence in Xinjiang, elsewhere in China or in neighbouring Central Asian countries.
China is accused of using the 'war
on terror' to persecute Uyghurs
But Raxit questioned why Beijing had never before publicized these concerns and accused China of applying double standards.
"Every ethnic group has its criminals. Hans [the majority Chinese] often mistreat Uyghurs. Sometimes there are confrontations which are hard to avoid. But you can't say they are terrorists," Raxit said.
"The Chinese government can't consider all opposition as terrorists. If they do, then why don't they consider Tibetan separatists and Falungong members as terrorists, why consider us? It's because our religion is different from that of the Chinese."