In an unusual move, Chinese authorities publicly said Muslim separatists who carried out terrorist attacks in western province of Xinjiang over the weekend were trained in terror camps in Pakistan.
Pakistan, seen as one of China's closest allies in Asia, is rarely criticised in public by Beijing. The most recent terrorist attacks left 11 dead, including five suspected militants who were members of China's Uighur minority.
The violence, which follows intermittent unrest and incidents of terrorism in Xinjiang over the past few years, may have tried China's patience.
Terrorism analyst B Raman has written that Chinese leader Hu Jintao is believed to have phoned Pakistani President Asif Ali Zardari last month and expressed concern about Chinese militants training in Pakistan and infiltrating back.
Islamabad, already in trouble with its other major ally, the US, was quick to assure Beijing of its "full support" against terrorists.
Local Chinese authorities issued a statement, saying suspects who were captured admitted to explosives and firearms training in "overseas camps" and that their commanders were trained in Pakistan.