Chinese artist Ai Weiwei said Monday thousands of supporters had donated four million yuan ($635,000) towards his tax fine, with some folding money into paper airplanes and throwing it into his garden. The drive to donate to Ai, who disappeared into custody earlier this year for 81 days and has since been ordered to pay a 15 million yuan tax bill, began Friday and has gathered momentum with more than 10,000 people giving money. "As of today, we have received about four million yuan," Ai told AFP. "The postal bureau has just notified me that there are 776 cash remittances that we need to go and pick up." But the state-run Global Times newspaper suggested Monday in an editorial that experts could charge Ai with "illegal fundraising" for accepting contributions for the tax bill he has to pay by November 15. The 54-year-old has denied any wrongdoing and insists the government is trying to silence him and his vocal human rights activism by accusing him of tax evasion. Supporters have been sending him money through Internet and bank transfers, while some have even resorted to throwing cash over the walls into his courtyard home, he said. "Every morning we have to pick up the money thrown into the courtyard. Sometimes they are folding it into planes or boats," he said. Ai's custody in April raised an international uproar, as scores of activists were rounded up amid anonymous calls on the Internet for street protests in China similar to those that toppled governments in the Arab world. He had earlier incensed the government by organising independent investigations into the collapse of school houses in the 2008 Sichuan earthquake and into a 2010 fire at a Shanghai high-rise that killed dozens. Ai, whose art works have sold worldwide -- some reportedly for hundreds of thousands of dollars -- admitted he did not need the money. "What I need is the ethical support of everybody. I don't need the money," he said. He has insisted the donations are a form of a loan which he has vowed to pay back.