Chinese experts are investigating an outbreak of respiratory illness in the central city of Wuhan that some have likened to the 2002-2003 SARS epidemic.

The city's health commission said in a statement Tuesday that 27 people had fallen ill with a strain of viral pneumonia, seven of whom were in serious condition.

It said most had visited a seafood market in the sprawling city, apparently pointing to a common origin of the outbreak.

Unverified information online said the illnesses were caused by severe acute respiratory syndrome, which emerged from southern China and killed more than 700 people in several countries and regions.

SARS was brought under control through quarantines and other extreme measures, but not before causing a virtual shutdown to travel in China and the region and taking a severe toll on the economy.

However, the health commission said the cause of the outbreak was still unclear and called on citizens not to panic.