Pope Francis led a years-long effort to build ties with authoritarian China and in 2018 the Holy See reached a two-year agreement with Beijing.

What is the Vatican-China deal?

The agreement allows China's communist government to nominate bishops for the pope's approval, giving both sides a say over church leadership.

In a key concession, Pope Francis recognised eight Beijing-backed bishops who were previously excommunicated because they were ordained without papal approval.

The deal -- the details of which were never fully disclosed -- was extended in 2020 and will be up for review this October.

Why was the deal made?

The 2018 provisional deal was an attempt to close the schism in China's Catholic population, previously estimated to be around 12 million.

China severed ties with the Holy See in 1951, forcing Catholics to choose between membership of the state-run Chinese Catholic Patriotic Association or underground churches loyal to the pope.

The Communist Party is officially atheist and exercises strict control over all recognised religious institutions, including vetting sermons.

Why was it criticised?

While some hailed the 2018 deal as a pragmatic compromise enabling dialogue, others fear that China's underground churches will become even more marginalised.

Those who operate without the Communist Party's blessing say they have been targeted by authorities in recent years, pointing to the demolition of underground churches, persecution of members and pressure on their clergy to switch sides.

The 2018 deal was also inked at a time when China was carrying out mass incarcerations of Muslims in its far-western Xinjiang region, a campaign the United States and multiple Western legislatures have declared a genocide.

After the deal was renewed, a commentary in the Holy See's official newspaper acknowledged "many situations of great suffering" in China, adding that the Vatican encourages a "more fruitful exercise of religious freedom".

The United States in 2020 opposed the deal's renewal, with then-secretary of state Mike Pompeo saying the Vatican would "endanger its moral authority".

Another vocal critic was Hong Kong's Cardinal Zen who accused the Vatican of "selling out" China's underground Catholic community.

Zen was arrested this month on national security grounds in Hong Kong. The charges are not linked to his criticism of the deal.

- What are the restrictions on religion in China? -

Under the leadership of President Xi Jinping, Chinese authorities have tightened their hold on religious groups despite warmer relations with the Vatican.

Xi has repeatedly called on foreign religions to undergo "Sinicisation", aligning their beliefs with Chinese culture and socialist ideology.

Underground Catholic clergy who refuse to comply with state demands have been subject to "detention, surveillance, and removal from active ministry" even after the Vatican deal, according to a report this year by the US Congressional-Executive Commission on China.

In January 2021, Chinese authorities imposed new rules on clergy management that put two state-run organisations in charge of appointing bishops, with no mention of papal authority.

The China-Vatican relationship is also closely watched in Taiwan, as the Holy See remains the sole European ally to officially recognise the self-ruled island.

China sees Taiwan as a part of its territory to be seized one day, by force if necessary, and has steadily convinced Taipei's diplomatic allies to switch recognition to Beijing.