Oil prices rose on Friday as the International Energy Agency forecast demand would climb faster than expected as the world economic outlook improves. But the IEA, which advises countries on energy policy, also noted that the crisis in Ukraine could still drag down overall consumption. Markets are additionally on alert over slower growth in China, the world's biggest energy consumer, that could result in downward pressure for prices. New York's main contract, West Texas Intermediate for delivery in April, rose 58 cents to $98.78 a barrel compared with Thursday's close. Brent North Sea crude advanced 19 cents to stand at $107.58 around midday in London. The IEA's latest demand estimate of 92.7 million barrels per day is an increase of 95,000 barrels a day above last month's forecast, with emerging markets expected to provide most of the gain, the agency said. Apart from a jump in prices on March 3, oil markets have been relatively calm despite the standoff between the West and Russia over Ukraine since February 22, when a wave of street protests ended up ousting Ukraine's pro-Kremlin president Viktor Yanukovych. Since then, Russian troops have seized control of Crimea, a small peninsula home to a mainly ethnic Russian population. The region will hold a referendum on Sunday to decide if it will join Russia or remain in Ukraine. Concerns remain however that potential Western sanctions against Russia could disrupt oil supplies from the country, a major energy producer and exporter of natural gas to Europe. More than 70 percent of its gas and oil exports to Europe pass through Ukraine.