The number of assisted deaths carried out by the Swiss association Dignitas rose by 35 percent last year, it was reported on Sunday.

A total of 144 people ended their lives in 2011 with the help of the clinic based in the canton of Zurich, according to police figures quoted by the Sonntags Zeitung newspaper.

All but five were of foreign nationality. The paper did not give the 2010 case total.

Dignitas helps people end their lives by supplying a lethal dose of a drug.

"Passive" assisted suicide is permitted under Swiss law provided it is not motivated by self-interest.

Active assistance, including helping the person to take the drug or administering it, is forbidden however.

Exit, another Zurich group providing assisted suicide, also saw its case number rise by about 17 percent last year, from 257 to more than 300, according to the article.

"Most people are suffering from cancer," Exit vice-president Bernhard Sutter told the paper.

Sutter said the average age of people choosing assisted suicide was 76.

Exit only assists those who are permanently resident in Switzerland, unlike Dignitas which has over the past decade offered more than 1,000 foreigners the opportunity to take advantage of Swiss law.

Voters in Zurich last May voted against plans to restrict assisted suicide to local residents.