KATHMANDU (AFP) - A Nepalese court convicted a Canadian orphanage volunteer on Sunday of sexually abusing a 15-year-old disabled boy and sentenced him to seven years in prison, an official said.

Ernest Fenwick MacIntosh, 71, arrived in the Himalayan nation on a tourist visa last August and approached the Jesuit-run St Xavier's Social Service Centre for homeless children with an offer of donations.

A court statement released after his conviction said MacIntosh repeatedly molested the boy, who has only one arm and was living in the orphanage, after offering him gifts and money and promising to pay for a prosthetic arm.

"He has been proven guilty and sentenced to seven years in jail... the boy's testimony and results of a polygraph test provided strong evidence against him," court spokesman Kaushaleshwor Gyawali said.

Police arrested MacIntosh after the boy filed a complaint on December 19.

MacIntosh has also been ordered to pay US$10,000 (S$13,638) in compensation to the victim.

The case underscores problems facing Nepal's orphanages, some of which have been hit by allegations of sexual abuse, corruption and fraud in recent years.

Although it is illegal to volunteer in Nepal on a tourist visa, orphanage officials often allow foreigners to spend time with children in exchange for donations. Background checks are rarely conducted on those offering to help.

In August 2012, Briton Simon Jasper McCarty pleaded guilty to sexually abusing three boys whom he met in Nepal. In December 2010, French charity worker Jean-Jacques Haye was convicted of raping 10 children in a Kathmandu orphanage.