BEIJING, China -- A COVID-hit Chinese city is offering thousands of dollars for anyone giving clues in tracing the source of its latest outbreak, as part of a "people's war" to stamp out one of the country's largest resurgences in months.

China reported 43 local cases on Tuesday in a Delta-driven surge that has fanned out to 20 provinces and regions, keeping new case numbers in the double-digits over the past three weeks.

As more countries lift Covid measures, Beijing officials have stuck stubbornly to a zero-Covid strategy that has maintained low infection numbers due to strict border closures, targeted lockdowns and long quarantines.
But the current outbreak has hit more than 40 cities, and officials in Heihe -- a northern city on the border with Russia -- said they would offer 100,000 yuan ($15,500) as a reward for information.

"In order to uncover the source of this virus outbreak as soon as possible and find out the chain of transmission, it is necessary to wage a people's war of epidemic prevention and control," the city government said in a notice.

Officials said cases of smuggling, illegal hunting and cross-border fishing should be reported immediately, adding that those who have bought imported goods online ought to "immediately sterilise" them and send them for tests.
The latest wave has seen millions put under lockdown and domestic travel rules tightened, with many planes and trains cancelled.

A cluster in central Henan province has been linked to schools, as health authorities urged more rapid vaccination of children.

Over 3.5 million vaccine doses have been given to children aged between three and 11, according to official data.

Beijing's rigorous anti-virus stance -- which has been used as political capital to extol the virtues of China's leadership -- has started to draw more public debate in recent weeks.

In an interview with Phoenix Television being shared on Chinese social media, virologist and University of Hong Kong professor Guan Yi appeared to call for better data to evaluate China's vaccine efficacy.

"We should not be carrying out mass nucleic acid tests at every turn" to detect Covid-19 cases, or blindly taking booster jabs, he said.

He instead urged antibody tests and timely updates by vaccine makers on the effectiveness of their jabs against variants.

The country has five conditionally approved vaccines, but their published efficacy rates -- varying between around 50 and 82 percent -- lag behind rival jabs from Pfizer-BioNTech and Moderna.

The official Xinhua news agency has lashed out against critics of China's approach, saying "strict containment measures are still the best way to save lives" and calling Beijing's efforts "unquestionable".