MUMBAI, April 26 -- India has ramped up purchases of Russian oil and revived alternate supplies from Africa, Iran and Venezuela to blunt a sharp crude shortfall from the crisis-ridden Middle East, analysts say.

India, the world's third-largest oil buyer, normally sources about half of its crude through the Strait of Hormuz, a vital waterway that has seen only a trickle of traffic since the United States and Israel launched attacks on Iran on February 28.

India's heavy import dependence, combined with modest oil reserves compared with major consumers like China, has prompted analysts to warn that India could be among the most vulnerable to a sudden oil price hike.

But while India is grappling with disruptions to cooking gas supplies, it...