The retired Bishop of Hong Kong has urged China to end the persecution of Christians in the country, according to UCA news.

Cardinal Joseph Zen Ze-kiun lead a prayer service in front of China's Hong Kong liaison office in Beijing, where around had 100 people gathered on April 24.

"Facing all this persecution, we cannot take it for granted. We cannot stand idly. If we keep silent, we are accomplices," he said.

The service coincided with the conclusion of a petition campaigning for Pope Francis to pray for religious freedom and an end to religious persecution in China.

The campaign, headed by Hong Kong's diocesan Justice and Peace Commission (JPC), which was asking Francis to urge the Chinese government to stop removing crosses, had gained 800 signatures.

"We hope the Pope can include the cross-removal campaign and the two missing bishops in his prayers on the prayer day," Or Yan-yan, project officer at JPC, told ucanews.com.

The prayer day for China was established by Pope Benedict XVI in 2007.

The petition also asks Pope Francis to "inquire about the situation of... two bishops in your communications with the Chinese authorities".

The two bishops Or referred to are Bishop James Su Zhimin, 84, and Bishop Cosmas Shi Enxiang, 95.

"These two bishops... have been imprisoned for over half of their lives. They have been forcibly disappeared for 18 and 15 years," the petition states.

The Communist Party is believed to be becoming progressively more suspicious of the influence of Christianity, which is experiencing significant growth in the country. Up to 1,700 churches have been demolished or had their crosses removed in Zhejiang province, and a number of church leaders and their lawyers have been arrested and detained.