The resurgence of COVID-19 in the country's capital over the past week, infecting more than 100 people and raising fears of wider contagion, has been linked to the city's massive Xinfadi food center.

The Communist Party's top disciplinary body said the outbreak underlined the urgent need to improve sanitation standards and minimize health risks at markets.

"The epidemic is a mirror that not only reflects the dirty and messy aspects of wholesale markets but also their low level management conditions," the Central Commission for Discipline Inspection (CCDI) said in a report published on its website on Wednesday.

China's sprawling food markets have emerged as an ideal breeding ground for the coronavirus, which has now infected more than 8 million people worldwide. The first major cluster of infections was traced to the Huanan seafood market in Wuhan, where bats and other wild animals were believed to be on sale.

The CCDI report noted that most of the markets were built 20 to 30 years ago, when drainage and wastewater treatment was relatively undeveloped.

An Yufa, a professor at China Agricultural University, was cited in the report as saying the markets must follow international practice and implement origin tracing systems as well as documentation on storage, transport and sale.

Officials in Wuhan province took 3,000 samples from tools, chopping boards and drains in 114 farmers' markets and 107 supermarkets this week to check for potential new sources of infection. All came up negative, they said.

China has promised to ban the trade and consumption and wildlife in a bid to minimize disease transmission, though the use of wild animal products in traditional medicine will still be permitted.