BEIJING — Ai Weiwei, the dissident artist whose detention earlier this year stirred an international outcry, has been given two weeks to pay $2.4 million in back taxes and penalties, he said Tuesday.

Mr. Ai and his lawyers have repeatedly denied the accusations against him, claiming the tax case is simply cover for the government’s more chilling aim: to silence a provocateur who has become one of the most persistent and instantly recognizable critics of China’s ruling Communist Party.

“This is ridiculous,” Mr. Ai said in a phone interview on Tuesday. “This is not the way a great power should behave toward its citizens.”

The bill, which far exceeds the $770,000 officials originally cited as unpaid taxes, suggests that the government is continuing its campaign against Mr. Ai, a conceptual artist, architect and documentary filmmaker whose work frequently takes aim at injustice and official corruption in Chinese society.