HARBIN, June 4 (Xinhua) -- The northeastern Chinese city of Mudanjiang in Heilongjiang Province has enhanced its efforts to screen for novel coronavirus infections by expanding tests to over 690,000 people as of Thursday, local authorities said.

The nucleic acid tests were conducted free of charge for permanent and temporary residents in the urban areas, according to the municipal government.

The city has mobilized 1,196 people from medical institutions as well as community workers and volunteers to collect samples, it said.