China's Health Ministry issued a nationwide alert on Saturday calling on local authorities to stop the spread of a virus that causes hand, foot and mouth disease, after an outbreak killed 22 children.

The deaths were first reported in March in the city of Fuyang, in the eastern province of Anhui.

More than 3,700 people in Fuyang have been infected with the virus, up from Friday's official tally of 3,300, according to figures released by local authorities on Saturday.

The central government has warned that the number of cases may increase over the summer because the June-July period is considered peak season for the disease.

Enterovirus 71, or EV71, mainly strikes children under age 10.

The disease, spread by direct contact with nose and throat discharges or fluid from blisters, usually starts with a slight fever followed by blisters and ulcers in the mouth and rashes on the hands and feet.

In more severe cases, there can be swelling of the brain, pulmonary edema and paralysis.

The nationwide alert means Anhui's government has the power to quarantine patients and control traffic in and out of Fuyang, the state-run Xinhua news agency reported.

Beijing has also sent 32 health specialists to Fuyang and has instructed Anhui and neighbouring provinces to step up training of medical workers.