The lockdown in the city comes as millions of Chinese travel across the country for the upcoming Lunar New Year holiday.
"Without a special reason, city residents should not leave Wuhan," the central city's special command centre to combat the virus said on Thursday, according to state media.
The move is meant to "effectively cut off the virus spread, resolutely curb the outbreak and guarantee the people's health and safety," the notice said, according to Xinhua news agency.
A Wuhan resident said on social media site Weibo that they were on the "verge of tears" when they heard about the closures, BBC reported.
Earlier, on Wednesday, Chinese Vice Premier Sun Chunlan called for all-out efforts to curb the outbreak of the novel coronavirus in Wuhan.
During an inspection tour of the city, she visited the entry and exit checkpoints of the Wuhan Tianhe International Airport, as well as the Hubei Provincial Center for Disease Control and Prevention, where she was given detailed reports on disease source detection, outbreak situation, scientific research and the stockpile of emergency supplies.
Chinese health authorities on Thursday announced that 571 confirmed cases of pneumonia caused by the novel coronavirus (2019-nCoV) had been reported in 25 provincial-level regions in the country by Wednesday.
Several regional airlines - including Malaysia's AirAsia and Singapore Airlines' budget carrier Scoot - have announced a temporary halt to flights to and from Wuhan.
( With inputs from IANS )