* Bill Clinton among those attending
* Government playing down anniversary this year
* 350,000 quake victims still homeless (Adds new lead, detail on Clinton Foundation effort in Haiti)
By Susana Ferreira
PORT-AU-PRINCE, Jan 12 (Reuters) - Haiti marked the third anniversary of the earthquake that destroyed much of the capital and killed more than 250,000 people with a purposely low-key commemoration on Saturday that included former U.S. President Bill Clinton.
Clinton, who is the U.N. special envoy for Haiti, joined the country's president, Michel Martelly, for a simple wreath-laying ceremony held at a mass burial site on a barren hillside at the outskirts of Haiti's capital, Port-au-Prince.
"Today we're here so that we don't forget, and to do better," Haitian Prime Minister Laurent Lamothe told reporters. "We were heavily hit, that's true. But we're standing strong to rebuild our country."
Earlier in the day, Haiti's government marked the occasion with a subdued ceremony on the grounds of the razed national palace in downtown Port-au-Prince. In a short address, Martelly paid homage to those who perished and praised the courage of those who survived.
"A little more lonely, a little more vulnerable," Martelly said. "I express to you my compassion."
He thanked donors and international aid organizations, and reassured them that the ongoing reconstruction effort would be closely evaluated to avoid waste and corruption. "I understand your concern," he said.
Martelly also announced the launch of a new building code, vowing that another tragedy like that of 2010 would never happen again.
This year's anniversary was a marked change from the hours-long commemorations organized by the government the first two years. The previous anniversaries included live musical performances, prayers from Haiti's spiritual leaders and press conferences.
Three years after the massive earthquake, reconstruction progress has been painfully slow, and barely half of the $5 billion in aid pledged by donors has been delivered.
About 350,000 displaced earthquake victims still live in camps, with little relief in sight. Only about 6,000 permanent houses have been built.
SIGNS OF PROGRESS
Still, there are some visible signs of progress. Most of the rubble from collapsed buildings has been cleaned up, and some long-term development projects in Haiti's north were inaugurated in recent months, including a $300 million industrial park and an airport expansion to accommodate international flights.
More than 80 schools have been built by the Jamaica-based cellphone company Digicel. And in the town of Mirebalais in central Haiti, construction of a modern teaching hospital, built by the Partners In Health charity, was completed.
The Clinton Foundation says it has spent a total of $28 million in Haiti since the earthquake, including relief funds as well as development projects.
"I'm encouraged by the work that's being done on the airports, some of the road construction that's been built, but we still need a lot more infrastructure work," Clinton told Reuters after visiting a housing project for displaced earthquake victims and an agricultural and technical training center run by the Mission of Hope, an evangelical development group.
"From my point of view, keeping the investment coming in, dealing with the housing and unlocking the education, those are the things I'd like to see real progress on this year," Clinton added. (Editing by David Adams, Jackie Frank and Eric Beech)