China reported two more deaths on Thursday from a severe strain of hand, foot and mouth disease, bringing its toll from the outbreak to 30, all of them young children, Xinhua news agency reported.

Hand, foot and mouth is a common childhood illness, but the current outbreak has led to fatalities in China, mostly when linked with enterovirus 71 (EV71), which can cause a severe form of the disease, characterised by high fever, paralysis and meningitis.

China also reported an additional 4,000 cases of hand, foot and mouth, bringing the total to nearly 20,000 across the country this year, but said the rise was due to better reporting of the outbreak, not the spread of the disease.

"The rising number is not a sign of a deteriorating situation," Xinhua said.

The two latest deaths were both on China's southern island province of Hainan, a tropical area popular with tourists.

The outbreak has centred on Fuyang city, in the poor, eastern province of Anhui, were 22 have died, but several other regions have reported fatalities.

Some 104 patients in Anhui remained in a critical condition, Xinhua said.

The World Health Organisation has said that China was not facing a new or more virulent strain of hand, foot and mouth, despite an unusually high number of child deaths.

But questions remain about why there has been such a large cluster of cases in Fuyang and why they presented unusual symptoms that made it difficult to identify the virus - a delay that may have cost lives.

Around Asia, cases of the disease, which mostly affects children under five, were at higher than usual levels.

Health experts say the peak season for hand, foot and mouth is usually June and July, meaning the number of cases could yet rise.