China acknowledged Thursday that anti-government riots have spread to other provinces after sweeping through Tibet last week, as Communist authorities announced the first group of arrests in the violence. The Foreign Ministry, meanwhile, said it was "seriously concerned" about a planned meeting between British Prime Minister Gordon Brown and the Dalai Lama, telling Brown not to offer support to Tibet's exiled Buddhist leader. Armed police and troops poured into far-flung towns and villages in Tibetan areas of adjacent provinces to reassert control as sporadic demonstrations continued to flare. Foreigners were barred from traveling there and tour groups were banned from Tibet, isolating a region about four times the size of France. The protests against Chinese rule started peacefully in Tibet's capital, Lhasa, early last week, but erupted into riots last Friday. Authorities say 325 people were injured and 16 people died - including three protesters who allegedly jumped from windows while trying to escape police.