COLOMBO (Reuters) - Sri Lanka’s former defense secretary Gotabaya Rajapaksa, who oversaw the crushing of Tamil Tiger rebels under his brother Mahinda Rajapaksa’s rule a decade ago, is being sued in two cases in the United States for his alleged role in torture and murder, according to a lawyer and court documents.

Sri Lanka's Secretary of Defense Gotabaya Rajapaksa listens during a news conference in Colombo January 24, 2013. The Sri Lankan military should be given more training opportunities by the United States, Rajapaksa said on Thursday according to local media. REUTERS/Dinuka Liyanawatte (SRI LANKA - Tags: HEADSHOT MILITARY POLITICS)

Gotabaya, popular among many Sri Lankans for his role in winning a 26-year war that ended in 2009, has expressed interest in running for president in elections later this year.

Since the end of the war Gotabaya has been accused by rights groups of multiple crimes during the civil war, including extrajudicial killings. He has rejected the allegations.

Milinda Rajapaksha, Gotabaya’s spokesman, said the former defense secretary has yet to receive “any official document or notice” on the cases.

“We see this as pure political revenge, part of propaganda designed to tarnish his image by vested interests for their own political mileage,” Rajapaksha told Reuters, without elaborating.

The South Africa-based International Truth and Justice Project (ITJP), in partnership with U.S. law firm Hausfeld and human rights lawyer Scott Gilmore, filed a civil damages case in California this week against Gotabaya on behalf of a Tamil torture survivor, Roy Samathanam.

The case alleges that Samathanam was detained in the capital Colombo in September 2007 by the Terrorism Investigation Division of the Sri Lanka police, who reported directly to Gotabaya, and was physically and psychologically tortured and forced to sign a false confession before being released in August 2010.

“Samathanam had no options left to seek justice in Sri Lanka or at the United Nations,” Gilmore told Reuters. “That’s why we brought the case in the United States when we found Gotabaya Rajapaksa returning to California.”

Gotabaya, a dual U.S.-Sri Lanka citizen, is planning to renounce his U.S. citizenship as required by Sri Lankan law to run for president, his close allies have told Reuters. His spokesman did not confirm this.

The case, filed in U.S. District Court for the Central District of California, was brought under the Torture Victim Protection Act, which gives torture victims legal redress in U.S. courts, Hausfeld said in a statement.

A statement from ITJP said that Gotabaya was formally served with notice of the case in a supermarket parking lot in Pasadena, California on Sunday after being tracked by private investigators.

In a separate case, Ahimsa Wickrematunga, the daughter of murdered investigative editor Lasantha Wickrematunga, filed a complaint for damages on April 4 in the same U.S. District Court in California for allegedly instigating and authorizing the extrajudicial killing of her father, documents seen by Reuters showed.

In her complaint, Ahimsa said that after the murder of her father in January 2009 Gotabaya and his allies obstructed her “efforts to seek justice in Sri Lanka by tampering with witnesses and engaging in a pattern of coercion and intimidation”.

Wickrematunga, an outspoken editor of The Sunday Leader newspaper, often clashed with politicians including Gotabaya.