BEIJING--Police raided a church in western China and detained 51 Christians, later sentencing one church member to 10 days detention, a US-based monitoring group and police said Tuesday.

The China Aid Association said police in Urumqi, a city in Xinjiang province, raided a house that lodged a church on Friday, detaining the Christians and releasing 48 later that day.

Two people, Zhu Jinfeng and Yang Miaofa, were briefly held by police. Yang was released after paying a 500 yuan ($73) fine. A third person, Zhou Li, was sentenced to 10 days of administrative detention, the group said.

At the Shayibake District Public Security office, a man named Tu'ersen confirmed the police raid.

The group said the three were church leaders, but Tu'ersen said Zhou, Zhu and Yang were detained only because they were the oldest members.

He said he did not know whether they had been released.

China allows Christianity but wants to channel it into state-backed churches. Still, religious activity is expanding, putting officials and police on the defensive.