Chinese authorities have banned churches "to create a safe environment" when world leaders arrive in the eastern city of Hangzhou for the G20 summit in September, according to local reports.

Global heads of state will fly into the capital of Zhejiang province for the annual two-day meeting which will be hosted by Chinese president Xi Jinping. Officials have declared a week long public holiday over the event to reduce congestion but religious worship has also been barred.

The Global Times, a tabloid run by the ruling Communist party, said large-scale religious meetings had been blocked "to create a safe environment for the meeting".

The US-backed Radio Free Asia reported that the city's unofficial churches had also been told to stop meeting. "They have been forcing house churches not to meet ahead of the G20 summit," said Zhang Mingxuan, the president of China's House Church Alliance.

But there is suspicion this move has more to do with China's targeted crackdown on churches in the Zhejiang than with the world leaders' arrival.

"I cannot understand why they have done this... Worshipping God has nothing to do with the G20 summit," said Li Guisheng, a Christian human rights lawyer, who added the move had no basis in Chinese law.

More than 1,200 places of worship have been attacked and had their cross removed in the province, which has the largest Christian population in the officially-atheist communist state.

A number of opponents have been detained amid the ongoing dispute. One well-known pastor, Gu Yuese ,was only recently released after being arrested in January for criticising the cross-removal campaign.

The UK Foreign Office has admitted China's house churches have faced "sustained pressure" from the Chinese government in a report on Friday.