Hollywood star Martin Sheen has declared himself proud of his uncle's IRA past.

The actor said he was also relieved to discover that his mother's brother, Michael Fieland, from Co Tipperary, had no part in the assassination of revolutionary leader Michael Collins.

Mr Sheen found out about his close family links to Ireland's War of Independence while taking part in the US version of the hit genealogy television series 'Who Do You Think You Are?'.

During the making of the programme, the 71-year-old visited Kilmainham Jail in Dublin and spent time in the cell where it is believed his uncle was incarcerated.

"I'm enormously proud of him," he said.

"I would like to hope that if I had been here in Ireland at the time, I would have followed him.

"And I would have been as committed as he was."

Best known for his roles in 'Apocalypse Now', 'Wall Street' and the television series 'The West Wing', he described his uncle as an Irish volunteer.

The actor said Mr Fieland went on to fight against the Free State side during the resulting Civil War in the early 1920s.

Mr Sheen admitted he was concerned about what would turn up during the trawl through his family past.

"When I was in Ireland and discovering the involvement of my uncle in the Rising and the Civil War . . . I was afraid he might have been in on the plan to assassinate Mick Collins," he said. "But as it turned out he was in prison when Mick Collins was assassinated and I was deeply relieved."

Known for his social activism, Mr Sheen added: "I have been involved in a lot of campaigns for peace and social justice and I had the same kind of commitment in those areas that he had here."

One of 10 children, Mr Sheen, whose real name is Ramon Estevez, was born to a Spanish father and Irish mother, Mary-Anne Fieland, from Borrisokane in Co Tipperary.

She emigrated to the US during the War of Independence, and he believes she was sent away to protect her from the intense hostilities. She was meant to come back when the fighting stopped and the Republic was established in 1923, he said.

"And so it was a very, very satisfying moment for me to know that she, too, was involved."