Jan. 26 (Bloomberg) -- Former United Nations Secretary- General Kofi Annan called for a probe into ``gross'' human rights violations in Kenya and violent ethnic clashes that have killed more than 680 people.

``There is gross and systematic abuse of human rights,'' Annan told journalists in Nairobi today after a visit to the conflict-torn western Rift Valley. ``I would hope serious investigations will be made to establish the facts and those responsible punished.''

Violence has gripped Kenya since President Mwai Kibaki was declared the winner in Dec. 27 elections that opposition leader Raila Odinga said were rigged. Annan, who is leading efforts to end the fighting, visited western Kenya, the main area of ethnic clashes, with former Tanzanian president Benjamin Mkapa and Graca Machel, wife of former South African President Nelson Mandela, Agence France-Presse reported.

``Certain groups are being targeted and that is unacceptable,'' Annan said. ``The government will have to do whatever it can to increase security and help these people get back home.''

Kibaki and Odinga met on Jan. 24 and agreed to try to halt the fighting, which has exposed ethnic tensions in a country previously regarded as stable. Annan helped set up the meeting to end tension that has driven more than 250,000 people from their homes and caused $1 billion in damage to the economy.

Kibaki, 76, belongs to the Kikuyu, the largest ethnic group, which makes up about a fifth of the population, while Odinga, 63, is a member of the Luo, who make up more than a 10th of Kenya's 35 million people. The U.S., the European Union, the U.K. and its former colonies and the East African Community have expressed concern over irregularities in the polls.

To contact the reporter on this story: Vernon Wessels in Johannesburg at vwessels@bloomberg.net

Last Updated: January 26, 2008 10:08 EST