Jan 17 (Reuters) - Most stock markets in the Gulf rose in early trade on Monday, in line with rising oil prices, with the Saudi index hitting its highest mark in over 15 years. Oil prices, a catalyst for the region"s financial markets, gained ground as investors bet supply would remain tight amid restrained output by major producers, with global demand unperturbed by the Omicron coronavirus variant. Brent crude futures were up 40 cents, or 0.5%, at $86.46 a barrel by 0641 GMT, touching their highest in more than three years. Saudi Arabia"s benchmark index (.TASI) edged up 0.1%, to its highest since July 2006, helped by a 1.2% rise in Saudi Telecom Company (7010.SE) and a 0.4% increase in oil giant Saudi Aramco (2222.SE). Saudi Energy Minister Prince Abdulaziz bin Salman said on Monday that it was up to the United States whether or not to release more supply from its strategic petroleum reserves. read more Dubai"s main share index (.DFMGI) added 0.1%, with Dubai Investments (DINV.DU) advancing 1.5% and Amlak Finance (AMLK.DU) rising 2%. In Abu Dhabi, the index (.ADI) was up 0.2%. The Qatari index (.QSI) gained 0.2%, led by a 1.4% increase in Qatar National Bank (QNBK.QA). Last week, the Gulf"s biggest bank reported a 10% increase in annual net profit driven by loan growth. read more However, Qatar Islamic Bank (QISB.QA) fell 0.8%, despite reporting a rise in annual profit.