Police surrounded a Chinese village on Sunday to prevent pilgrims from joining a Catholic parade to honour the Virgin Mary, who locals say appeared in the village a century ago.

Authorities placed roadblocks on main roads leading to the small village of Donglu, just a few hours drive from Beijing, where locals -- an estimated 90 percent of whom are Catholic -- are fiercely devoted to Mary.

"Police don't let any outsiders into the village during May... it's been like that for years," a local believer who identified herself as Maria said, standing by the towering spires of a church which dominates the village's skyline.

Donglu's Catholics believe that the Virgin Mary appeared in the sky above the village in 1900, terrifying attackers from the anti-foreign Boxer uprising, which also targeted Catholics, into an awestruck retreat.

"More than 100 years ago, everyone felt the power of Mary to protect the village, and each generation has passed on the story," Maria said.

A police lock-down lasting the entire month of May, when celebrations dedicated to Mary reach their peak, was established in the 1990s, after tens of thousands of pilgrims from China and abroad gathered in the village, locals say.

More than 30,000 Catholics took part in celebrations in the village in 1995, prompting local authorities to mobilise thousands of troops, arrest priests, and demolish a shrine to the Virgin Mary, according to Catholic activist websites.

AFP reporters -- who entered the village through tiny back lanes, before being briefly detained and escorted out by local police -- saw officers sitting in blue tents erected as checkpoints on access roads.

Red banners calling on locals to "carry out religious activities in a lawful and orderly manner" flapped in the breeze.

But celebrations dedicated to Mary continued despite the restrictions. Around 200 Catholics, including young children, gathered outside the village church on Sunday for the parade.

Locals waved bright flags while women in yellow silk dresses decorated with crosses climbed aboard a pick-up truck loaded with red drums, and two men held a large picture of Mary and Jesus in front of the crowd.

"The authorities are afraid that we will cause trouble, but the vast majority of Catholics would never cause trouble," an 81-year-old local surnamed La said.

Parishioners bowed in front of a statue of Mary, which had been covered with roses, before attending morning mass. "We pray for our church," the congregation said, their call echoing through the building's gothic arches.

Catholics in the village -- which has a population of roughly 10,000 -- said miracles continue to occur around the site of Mary's supposed appearance.

A parishioner passed AFP a photograph of a priest with red-hands holding a Eucharist, which locals claim bled the blood of Jesus during a mass last year.

"You should never rip or damage this picture, it's a gift from God," a woman said.

Though China's government controls on religion have loosened in recent decades, it remains wary of unofficial mass gatherings, fears some attribute to China's history of anti-government religious movements.

A Christian convert in the nineteenth century founded the "Taiping Heavenly Kingdom," gathering millions of followers in an attempt to overthrow the emperor.

China in 1999 launched a huge crackdown on the Falun Gong, a spiritual movement which held a mass gathering in Beijing, and was branded as an "evil cult" by the ruling Communist Party.

Police did not directly state why outsiders were unwelcome in Donglu.

"Tourism is not permitted here," local policeman Guo Lei said, before asking AFP reporters whether they were Catholics.

AFP was told by villagers that the lock-down usually proved successful in deterring potential visitors.

China has repeatedly said that its citizens enjoy freedom of religious belief, but Catholic rights groups have for years reported police repression of "underground" churches, which operate without government approval.

Experts estimate that there are around 12 million Catholics in China, with about half worshiping in state-sanctioned congregations, and the rest belonging to unofficial churches.

Church officials in Donglu said they often met the demands of local officials in order to continue their worship. They said they won a slight increase in freedoms in recent years, though they complained about the blockade.

"In this area, reasonableness doesn't matter," one Church official, who did not want to be named for fear of reprisals, said. "The government does what it wants, regardless of reasonableness, or fairness."