Quarantine at centralised facilities has been cut to seven days from 14, and subsequent at-home health monitoring has been reduced to three days from seven, the National Health Commission said in a statement.
The latest guidelines from the health authority also eased quarantine requirements for close contacts of people who have tested positive for the new coronavirus.
China has cautiously eased its COVID curbs on cross-border travellers in recent months, with health officials saying the shorter incubation period of the Omicron variant allows for an adjustment of quarantine periods.
The Chinese capital Beijing in recent months has already reduced the quarantine period at centralised facilities to 10 days from 14.
China, last month, also removed some COVID-19 test requirements for people flying in from countries such as the United States.
Beijing and Shanghai reported on Tuesday no new local COVID infections, the first time both cities were in the clear simultaneously since late February, after months of fighting their worst-ever outbreaks.
The milestone for the two cities, achieved on Monday, came after their daily caseloads dropped to single digits over the past week, allowing Shanghai to gradually resume eating in at restaurants and Beijing to reopen some leisure venues including the Universal Beijing Resort.
Shanghai Communist Party chief Li Qiang declared on Saturday that authorities had "won the war to defend Shanghai" against COVID-19, after a crushing two-month citywide lockdown that was finally lifted in early June.
The Walt Disney Co's Shanghai Disney Resort said on Tuesday that it would reopen the Disneyland theme park on June 30; it had been shut for more than three months.
Authorities, however, remained wary and were adamant that the government's so-called dynamic zero COVID policy, which aims at blocking flare-ups from spreading as they crop up, remains in place.
Beijing would "fight against any new outbreaks at the outset and with speed and resolutely break their transmission channel", Cai Qi, the city's top Communist Party chief, was quoted as saying in a report by the party-backed Beijing Daily.
The city would build "a solid virus barrier", Cai was quoted as saying on Monday.
Despite easing COVID restrictions in Beijing and Shanghai, their combined 47 million residents have been told to go through COVID testing every few days, to maintain access to public spaces and transport.
Elsewhere in mainland China, a total of 22 domestically transmitted infections were reported for June 27, including five in the southern technology hub Shenzhen.Â
