Mass protest at funeral of slain Sri Lanka editor

COLOMBO, Jan 12 (Reuters) -- Thousands marched in the funeral procession of a slain Sri Lankan newspaper editor in the capital Colombo on Monday, demanding the government punish those responsible to ensure media freedom and democracy.

A packed crowd gathered at the entrance of Sri Lanka's main cemetery in one of the largest protests in recent memory, blocking roads and vowing to fight until democracy was restored.

Sunday Leader Chief Editor Lasantha Wickramatunga was gunned down in traffic on Thursday morning and died in hospital soon afterwards. The government promised a thorough investigation.

The United States, the European Union, Canada and India have all condemned the killing and demanded a swift investigation.

Diplomats, opposition politicians, journalists and rights activists all marched in the hours-long procession.

"This death is a serious blow to democracy and media freedom," opposition leader Ranil Wickremasinghe said.

Many mourners carried placards reading "End Tyranny, Defend Democracy!" or "Defend Democracy, Defend Dissent".

The opposition, which is anticipating a possible early election, has accused the government of responsibility for the attack. Some protesters burned an effigy of President Mahinda Rajapaksa and many wore black armbands.

Rajapaksa has said that international forces were behind the attack and were trying to distract attention from two major military victories against the separatist Tamil Tigers in the last two weeks.

Both he and Wickramatunga had said they were friends for decades, despite differing once Rajapaksa took office.

Wickramatunga repeatedly took on powerful political and business interests in Sri Lanka with critical reporting and investigative stories uncovering what the Sunday Leader said was corruption.

He was repeatedly sued for defamation by those he challenged.

Press freedom groups say the Indian Ocean island nation has major dangers for journalists, described on Sunday -- three days after his death -- in an editorial the Leader attributed to Wickramatunga entitled "And Then They Came For Me".

"No other profession calls on its practitioners to lay down their lives for their art save the armed forces and, in Sri Lanka, journalism," the editorial said.

Amnesty International says 14 media workers have been killed in Sri Lanka, and Wickramatunga said in his editorial that he had long expected to join that list.

"Countless journalists have been harassed, threatened and killed. It has been my honour to belong to all those categories and now especially the last," the editorial said.

He was killed two days after more than a dozen gunmen destroyed the main studios of MBC Networks, Sri Lanka's largest independent broadcaster.

State-run media had days earlier criticised MBC's coverage of a suicide bombing on the day of a major military victory. (Writing by Bryson Hull; editing by Tim Pearce)