NEW YORK -- Crude prices rose slightly Monday amid escalated conflict in eastern Ukraine.

Tensions got worse after a Sunday morning shooting at a checkpoint in eastern Ukraine left at lease three people dead, and Ukrainian and Russian officials blamed each other for the incident.

Russia is the world's second largest producer of natural gas and it produced more than 10 million barrels crude a day in January. More than 70 percent of Russian crude and gas exports to Europe pass through Ukraine.

Traders are worried that the possible US or European sanctions might disrupt Russian oil exports.

On the economic front, the Leading Economic Index (LEI) for the US increased 0.8 percent in March to 100.9, following a 0.5 percent increase in February and a 0.2 percent increase in January, said the Conference Board, a New York-based business research organization, in a report.

Moreover, led by improvements in production-related indicators, the Chicago Fed National Activity Index increased to 0.14 in February from minus 0.45 in January, reported the Federal Reserve Bank of Chicago Monday.

Light, sweet crude for May delivery moved up 7 cents to settle at $104.37 a barrel on the New York Mercantile Exchange, while Brent crude for June delivery gained 42 cents to close at $109.95 a barrel.