SEOUL, Jan 14 (Reuters) - South Korea will extend tougher social distancing rules for three more weeks amid concerns over a looming wave of the highly contagious Omicron coronavirus variant especially ahead of the Lunar New Year holidays, officials said on Friday. The curbs were restored a month ago just six weeks after being eased under a "living with COVID-19" scheme, as record-breaking numbers of new cases and critically ill patients threatened to saturate the country"s medical system. Daily tallies have dropped since, with 4,542 new cases for Thursday from a peak of almost 8,000 in mid-December, but the downtrend appeared to bottom out this week due partly to a surge in Omicron infections. "The indicators have improved more or less but the number of new cases are no longer decreasing this week," Prime Minister Kim Boo-kyum told an intra-agency meeting, noting that Omicron"s share of domestically transmitted infections has reached 20% in just two weeks. The extended curbs will last until Feb. 6, including a 9 p.m. curfew for restaurants, cafes and bars, but the limit on private gatherings will be raised to six fully vaccinated people from four. Health officials have warned that without stricter distancing curbs Omicron would become dominant within two weeks, possibly sending daily tallies up to an unprecedented 20,000 in February and 30,000 in March. The Lunar New Year break begins on Jan. 29, and normally tens of millions of Koreans would travel country-wide for family gatherings during one of the country"s main holidays, raising the risks of contagion. As part of efforts to pre-empt Omicron"s spread, South Korea began treating patients with Pfizer"s (PFE.N) antiviral pills on Friday, becoming the first Asian country to do so. read more The government said on Friday it will submit a supplementary budget worth about 14 trillion won ($11.8 billion) to parliament later this month to support small businesses and the self-employed hit by the pandemic, adding to a record 607.7 trillion won ($511.5 billion) budget for 2022. The country of 52 million people has largely been a COVID-19 mitigation success story, with 683,566 total infections and 6,259 deaths, thanks chiefly to masks, distancing and aggressive testing and tracing. Nearly 95% of South Korean adults have been fully vaccinated and more than 50% have received a booster shot. South Korea has also rolled out one of the region"s most stringent vaccine pass mandates, under which unvaccinated people can only dine out alone, or use takeout or delivery services. ($1 = 1,188.4900 won)