BEIJING (AP) — A court in northwest China has rejected an appeal from a Tibetan environmentalist who was sentenced to 15 years in prison on charges of grave robbing and dealing in looted antiquities, his lawyer said Monday.

The charges against Karma Samdrup — named philanthropist of the year in 2006 by state broadcaster CCTV — date back to 1998 but were not pursued until this year. They stem from purchases he made of carpets, wooden artifacts and other antiques at a shop in Urumqi, the capital of Xinjiang.

Lawyer Pu Zhiqiang has said his client bought the items because he was interested in them as a collector, but did not know they had been plundered from graves in the region.

Supporters have said the June 24 trial was aimed at punishing Karma Samdrup after he spoke up for his two brothers who were detained after accusing local officials in eastern Tibet of poaching endangered species. Authorities in tightly controlled Tibet are extremely sensitive to social activism and criticism, either explicit or implied.

Pu, who complained of irregularities during the original trial, said he only learned Monday that his client's appeal had been rejected on July 7.

The Bayingolin Mongol Autonomous Prefecture Intermediate Court never responded to the documents he filed for Karma Samdrup's appeal and have not explained why they rejected it, he said. Pu also questioned why the appeal was rejected so quickly after the conclusion of the original trial.

"I don't know why they're in a such a hurry. What are they afraid of? What are they trying to cover up?" he said in an interview with The Associated Press.

Phones at the court rang unanswered Monday.