BEIJING (Reuters) - China on Thursday called on groups and individuals outside the country to actively encourage graft suspects who have fled overseas to give themselves up, and promised leniency for those who surrender.

President Xi Jinping has waged war on deep-seated corruption since assuming office six years ago, including going after those who have fled abroad to try to escape justice.

In April 2015, authorities published a list of 100 “most-wanted” suspects it believes to be hiding overseas, many in the United States, Canada and Australia. More than half have already come back to China, some voluntarily.

Five departments and ministries, in a joint statement carried on the website of the ruling Communist Party’s graft watchdog, said that until the end of this year they would be offering lighter sentences to those who gave themselves up, handed over evidence and returned pilfered funds.

Relatives and friends of suspects are encouraged to persuade them to return to China, and the notice made specific mention of those outside the country, though it did not explicitly call for foreign nationals or organizations to get involved.

“Encourage and protect the broad masses of the people and relevant overseas organizations and individuals to actively report, mobilize and persuade” those abroad to surrender, the departments and ministries said.

Those who provided useful information would get rewards, they added in their statement.

China has tried to get greater help from Western countries, in particular, to arrest and deport corruption suspects, but has upset some foreign governments by sending security officials covertly to carry out investigations on foreign soil.

Many Western countries have been reluctant to help with the Chinese campaign, or to sign extradition treaties, unwilling to send people back to a country where rights groups say mistreatment of criminal suspects remains a problem.

Some Western countries also complain China is often unwilling to provide proof of the crimes that would be acceptable to their courts.