Dec 27 (Reuters) - Most stock markets in the Gulf fell in early trade on Monday, with the Saudi index leading the losses, as uncertainty over the economic impact of the Omicron coronavirus variant weighed on investor sentiment. Coronavirus infections have started rising again across the six Gulf Arab states after months of low or falling figures, data from health ministries showed on Thursday. read more Saudi Arabia"s benchmark index (.TASI) dropped 0.7%, with Al Rajhi Bank (1120.SE) losing 0.6% and Saudi National Bank (1180.SE), the kingdom"s largest lender, retreating 1%. Saudi health authorities advised citizens and residents last week to avoid all unnecessary foreign travel. The kingdom reported its first Omicron case on Dec. 1. Oil prices, a key catalyst for the Gulf"s financial markets, fell after airlines called off thousands of flights in the United States over the Christmas holidays amid surging COVID-19 infections. In Abu Dhabi, the index (.ADI) edged 0.1% lower, hit by a 0.7% fall in Alpha Dhabi Holding (ALPHADHABI.AD). The United Arab Emirates (UAE) has seen a sharp increase in COVID-19 infections since announcing the arrival of Omicron early this month, with 1,803 cases of coronavirus recorded on Sunday, up from 68 on Dec. 2. The resurgence comes during the region"s peak tourism season, especially in the UAE which is welcoming millions of visitors to the Expo 2020 Dubai world fair and other seasonal events. Separately, the UAE government has told some of its biggest business families that it plans to remove their monopolies on the sale of imported goods, Reuters reported on Sunday, citing the Financial Times. read more Over the past year, the UAE, a growing economic rival of Saudi Arabia, has taken measures to make its economy more attractive to foreign investors and talent. Dubai"s main share index (.DFMGI) firmed 0.1%, helped by a 0.4% increase in blue-chip developer Emaar Properties (EMAR.DU). The Qatari benchmark (.QSI) eased 0.1%, with petrochemical maker Industries Qatar (IQCD.QA) declining 0.7%.