All Covid-19 pre-departure test results for travellers from India entering Singapore must come from recognised labs which are internationally accredited or endorsed by the Indian government, said Singapore's Ministry of Health (MOH).
Those without the required valid documents will not be allowed into the country.
Additionally, from today, all travellers - including Singapore citizens and permanent residents - with a recent travel history to India within the last 14 days before coming to Singapore will have to take a serology test. The test detects the presence of antibodies and can show if the person might have been infected.
Those who test positive will be exempted from taking the polymerase chain reaction swab test - which detects the presence of viral genetic material - before the end of their two-week stay-home notice (SHN) period.
The latest directive to produce valid pre-departure test results from recognised labs comes as faked test results are becoming increasingly common in India, with reports of agents and doctors taking bribes to produce them.
This requirement also follows a significant jump in imported cases from India, with the gradual easing of travel rules and loosening of the country's border restrictions.
In the five days from last Thursday to Monday, two-thirds of Singapore's imported cases, or 61 per cent of them, had visited India.
MOH said last Friday that there will be two levels of checks - one at the airport in India before boarding, and the other at the arrival immigration in Singapore.
"Travellers found without the required valid documents will be refused entry into Singapore. We will not hesitate to take action against those who present forged documents to seek entry into Singapore, including barring them from entry to Singapore in the future," warned the ministry.
This new and more stringent border restriction comes in addition to existing requirements - a two-week SHN period at dedicated SHN facilities and a further negative Covid-19 test before the end of the SHN period.
"This covers the full incubation period of Covid-19, and has been effective in preventing spread into our local community," MOH assured.