MOSCOW (Reuters) – Moscow began testing thousands of randomly-chosen residents for coronavirus antibodies on Friday under a mass screening programme authorities hope will help them determine when it is safe to lift the city’s lockdown restrictions.

The Russian capital of 12.7 million is in its seventh week of a shutdown and has shouldered the brunt of Russia’s outbreak, which has seen more than a quarter of a million people infected nationwide according to official figures.

Sergei Sobyanin, Moscow’s mayor, has said the real scale of the outbreak is much bigger than official data shows because many people will not have manifested symptoms and therefore not realised they are carriers.

Sobyanin said mass testing would help identify such people, paint a reliable picture of the outbreak’s spread, and allow officials to relax the lockdown without risking lives when the time was right.

Under the programme, around 70,000 residents will be invited every several days to undergo a free blood test at one of 30 different clinics across the city, Sobyanin said. They will be tested for the new coronavirus as well as for coronavirus antibodies.

People will be selected at random and invited by text message or by email. The test is voluntary. Those willing to undergo it will have to register online, officials say.

Moscow city authorities hope to develop an antibody testing system that will allow them to process 200,000 tests a day by the end of the month, Moscow’s mayor said.

(Reporting by Tom Balmforth; editing by Andrew Osborn)