Dec 23 (Reuters) - Most stock markets in the Gulf rose in early trade on Thursday, as investor sentiment improved after a study suggested the Omicron variant of COVID-19 might be less severe than feared. The South African study suggested reduced risks of hospitalisation and severe disease in people infected with the Omicron coronavirus variant versus the Delta one, though the authors said some of that was likely due to high population immunity. read more Saudi Arabia"s benchmark index (.TASI) gained 0.6%, with Al Rajhi Bank (1120.SE) rising 0.9% and petrochemical maker Saudi Basic Industries Corp (2010.SE) advancing 1.2%. Saudi Investment Bank (1030.SE) jumped 4.7%, adding to its more than 9% gain on Wednesday following a proposal to increase capital and distribute a dividend of 0.70 riyal per share for 2021. Separately, Saudi Arabia"s Capital Markets Authority said on Wednesday it had approved an initial public offering of digital security firm Elm, which is owned by the kingdom"s sovereign wealth fund. read more Dubai"s main share index (.DFMGI) added 0.1%, helped by a 0.4% rise in sharia-compliant lender Dubai Islamic Bank (DISB.DU). Meanwhile, MSCI"s broadest index of Asia-Pacific shares outside Japan (.MIAPJ0000PUS) rose 0.55%, a third consecutive session of gains as it recovered from a jolt on Monday when worries about the new coronavirus strain gripped markets. Oil prices, a key catalyst for the Gulf"s financial markets, also rose, buoyed by optimism about the state of the global economy. In Abu Dhabi, the stock index (.ADI), however, fell 0.4% and was on course for a fifth straight session of drop, with Emirates Telecommunications Group (ETISALAT.AD) losing 0.7%.