The "East Turkistan terrorists" refers to the separatist Turkic-speaking Muslim Uighurs and groups like the World Uighur Congress, who have been blamed for the July 5 ethnic violence in Urumqi, capital of the northwest Xinjiang-Uighur province, which the government says left at least 184 dead, 134 of them Han Chinese.
The WUC, based in Munich, Germany, has denied the charges.
"We firmly oppose any support for the 'three forces' by any foreign countries or overseas organizations and demand they immediately cease the support," Chinese Foreign Ministry spokesman Qin Gang said without naming the nations he said were financing the alleged terrorists.
Qin said evidence showed forces within China and outside have never stopped trying to sabotage China's national security and that "relevant countries" had provided them support and money, Xinhua reported.
The state-run Chinese news agency said U.S. State Department spokesman Ian Kelly acknowledged Monday a U.S. organization had provided funding for the WUC.
Qin said China and Muslim countries had forged relationships of mutual respect and support that "will move forward on the basis of ... mutual respect, equality and mutual benefit."
In a separate report, China Daily said China had alerted overseas Chinese and Chinese groups about threats from al-Qaida in the wake of the ethnic violence in Urumqi. The report said the alert was sent out a day after the Islamic terrorist group threatened to target Chinese interests overseas.