India's Omicron cases have risen to 21, with as many as 17 people testing positive for this new variant of Covid across the country in 24 hours, officials said Monday.

This is a sharp spike of 19 cases of the Omicron variant in just four days, despite the country ramping up efforts to contain its spead. India Thursday reported its first two known Omicron variant cases, discovered in two men in Karnataka state.

"In 24 hours till Sunday night, nine people in the northwestern Indian city of Jaipur, seven in the western city of Pune and a 37-year-old fully vaccinated man who arrived in the national capital from Tanzania tested positive for the new variant," an official said.

Read:India reports first two Covid cases of Omicron variant

Omicron has been classified as "a variant of concern" by the World Health Organisation. It was first discovered in South Africa.

Meanwhile, on Monday, India logged a total of 8,306 new Covid cases in 24 hours, taking the total caseload to 3,46,41,561, according to the latest Health Ministry data.

Last week, the Indian government backtracked on its decision to resume regular international flights from December 15, following an advice from Prime Minister Narendra Modi.

The Indian government put curbs on all domestic and international flights in March last year in the wake of the Covid-induced lockdown. However, it allowed domestic flights from May 2020, and the entry of all foreigners except tourists from October that year.