* Protesters number only a few hundred in Sri Lanka
* Unions say people put off by threat of layoffs
* Government says demonstrations simply failed
By Shihar Aneez and Ranga Sirilal
COLOMBO, May 21 (Reuters) - Sri Lanka's opposition parties and trade unions accused the government on Tuesday of threatening state employees with the sack if they took part in planned street protests against a sharp rise in electricity prices.
Only a few hundred people joined the demonstrations, coordinated by the political opposition and trade unions, despite expectations of much larger crowds on the streets of Colombo.
The government rejected the accusations, saying that the planned walkout had simply failed.
Sri Lanka has more than 1.3 million state sector employees out of a total population of around 21 million people, and any strike by them could cripple the $59 billion economy.
Major trade union action, including extended strikes, have led to governments being toppled in the past.
"The government has threatened the trade unions and workers by saying they will be kicked out of their jobs," John Amaratunga, a legislator from the main opposition United National Party, told parliament.
Chandrasiri Mahagamage, secretary of the All Ceylon Port Common Workers Association which is part of the Trade Union Alliance, said a top official was at the main entrance to the port holding a camera to intimidate protesting workers.
"The (port) management threatened to fire employees who took part in today's trade union action," he said.
Most trade unions affiliated to the opposition in state-run companies object to the government's decision to raise domestic electricity prices by up to 59.4 percent. The price hike came into effect on April 20.
President Mahinda Rajapaksa's ruling coalition, which has more than a two-thirds majority in parliament including some lawmakers who defected from the opposition, has not faced mass protests since it came to power in 2005.
The government's Information Department said that 93.5 percent of public sector employees showed up for work on Tuesday, 3.5 percent higher than the average daily attendance.
"We have not interfered or threatened," Deputy Plantation Industries Minister Earl Gunasekara told reporters. "A strike will cripple normal day-to-day life, but today everything functioned even better than on a normal day." (Reporting by Shihar Aneez; editing by Mike Collett-White)