Christianity has been present in China since at least the 7th Century AD and likely as early as the 1st Century AD. Once heavily restricted by the Chinese Communist Party, Christian practice is now permissible, though officially only under strict government sanctions. Any adult, 18 years or older, is allowed to participate in the meetings of two officially registered Christian organizations, the "Three-Self Patriotic Movement" or the "Chinese Catholic Patriotic Association." Most Chinese Christians participate in secret "house church meetings" which are technically illegal. There are reports of occasional crackdowns on these meetings and of persecution of Chinese Christians, which has been the cause of concern for international observers. The Chinese government reports that there are upwards of 14 million Christians in China, but independent estimates put the number between 40 and 130 million.