Oil prices rose in Asia today on increased geopolitical tensions as the United States hinted at fresh sanctions against Moscow after Crimea voted in a referendum to break away from Ukraine and join Russia. New York's main contract, West Texas Intermediate for April delivery, was up 23 cents to 99.12 dollar in mid-morning Asian trade, and Brent North Sea crude for May gained 11 cents to over 108 dollar.Investors are worried that potential sanctions against Russia could disrupt gas and oil supplies from the country. More than 70 per cent of Russia's gas and oil exports to Europe pass through Ukraine.