Natalya Lepyoshkina smiled as she fed her three-week-old "children" a meal of warm cow's blood, rinsed them off with water and poured them into an array of glass jars.

"They're happy, they're full," she said as the young leeches, squirming and swollen from their meal, settled into the containers that would be their home until the next feeding.

Lepyoshkina's charges were among the three million leeches raised every year at the International Medical Leech Centre, an institution founded in 1937 that touts itself as the world's largest leech-growing facility.

Located in Udelnaya, a village of humble wooden houses several kilometres (miles) southeast of Moscow, the centre is now enjoying strong sales as scientists reassess their attitude to the bloodsucking creatures.

Researchers, Western governments and even Hollywood stars have endorsed the use of leeches in recent years, after decades during which the practice fell into disuse and was regarded as a relic of medieval times.

The American Journal of Nursing wrote this year that leech therapy was having a "resurgence", mainly in helping patients of plastic and reconstructive surgery, and was useful for certain blood and tissue conditions.

The US government approved the use of leeches as medical "devices" in 2004, and the actress Demi Moore revealed last year that she had undergone leech therapy in Austria to "detoxify" her blood.

"Now this is a scientifically proven form of healing," Gennady Nikonov, the director of the Udelnaya leech centre, said in his office, near a wall covered with awards from European and Russian institutes.