COLOMBO (AFP) - Gunmen opened fire and torched the office of the main Tamil newspaper in northern Sri Lanka on Saturday, the owner said, the latest in a wave of attacks against privately-owned media in the country.

Three armed men carried out the pre-dawn arson attack on the Uthayan office and printing press in Jaffna, the city and former war zone 400km north of Colombo, owner Eswarapatham Saravanapavan told AFP by telephone.

"Employees preparing to deliver the morning newspaper fled as the gunmen stormed in... It has to be either the government or para-militaries. Who else can carry firearms freely in Jaffna?" Mr Saravanapavan said, adding there were no injuries but the printing press had been destroyed.

"Just last week we asked for security from the police after one of our offices was attacked elsewhere," he said, referring to a previous incident at another Uthayan office in the north.

There was no immediate comment from the authorities.

Mr Saravanapavan, who is also an opposition Tamil National Alliance (TNA) legislator, said he had lost at least five employees killed in attacks against the paper in the past eight years.

Saturday's assault came five days after the US ambassador in Sri Lanka, Ms Michele Sison, expressed concerns over media freedom and noted that those responsible for violence against the Uthayan had not been brought to justice.

"We urge the Sri Lankan authorities to fully investigate (last week's) Uthayan attack and hold the perpetrators accountable," Ms Sison told the Foreign Correspondents' Association on Monday.

In February, a journalist working for a privately-owned weekly in the capital was shot and wounded by an unidentified gunman.

There is no formal censorship in Sri Lanka, but rights groups say journalists practice self-censorship to avoid violence.

Sri Lanka lifted a state of emergency in Aug 2011 after defeating the Tamil separatists, but armed troops are still deployed in Jaffna and other parts of the country to support the police.

A total of 17 journalists and media employees have been killed in Sri Lanka in the past decade. No one has been brought to justice for the killings.

Jaffna, the cultural capital of the island's ethnic Tamil minority, was once run as a de-facto separate state by the Tamil Tigers who were crushed in a major military offensive that ended in May 2009.