Haitians marked the second anniversary of the earthquake that ravaged their impoverished Caribbean nation on Thursday, mourning the dead as their president held out hope for a better future.

Many women wore white dresses, and men turned out in dark suits, as they attended church services and held solemn ceremonies at mass grave sites across the deeply religious country.

The 7 magnitude quake on January 12, 2010, which lasted only 10 to 20 seconds, was one of the world's worst natural disasters. It toppled buildings and homes, killing roughly 300,000 people and making more than 1.5 million homeless.

President Michel Martelly has vowed to redouble government efforts to help people rebuild their lives and reverse a painfully slow recovery marked by squalid tent camps that are still home to more than a half a million people in the capital, Port-au-Prince.

This year is a year when we will really start rebuilding physically but also rebuilding the hope and the future of the Haitian people, the shaven-headed former Carnival music star known as Sweet Micky said on Wednesday.

In one of the main events of Thursday's remembrance, Martelly and former U.S. President Bill Clinton, who has promoted job creation to lift Haiti out of decades of misery and corruption, paid homage to the dead at Titanyen, a mass burial ground north of Port-au-Prince.

Tens of thousands of quake victims are thought to have been buried in unmarked graves at the site. Laid out across a vast open field, it had been a dumping ground for victims of dreaded death squads during the Duvalier family dictatorship.

'WHIMS OF NATURE'

Speaking at the site, Martelly said the quake was one of many catastrophes in a country run by ruthless despots for most of the 200 years since a slave revolt freed it from French rule.

Misery stems from more than just the deadly and disastrous whims of nature, he said.

In a country where people cannot get healthcare isn't that a catastrophe? he asked. In a country where children can't have access to school isn't that a catastrophe? In a country where people don't have access to potable water isn't that a catastrophe?

Despite billions of dollars of international donations and aid pledges, many Haitians say they see few tangible results of the recovery and reconstruction effort.

Almost half of the piles of concrete, steel and other debris that littered Port-au-Prince and its surrounding areas have yet to be cleared.

My hope is we will do everything we can to honour the memory of those who died by transforming the disaster into an opportunity to provide a better future for Haitians, said Junot Mura, a 23-year-old Port-au-Prince resident who said the quake took the life of his father.

Government officials point to post-quake projects like a $257 million industrial park being built on Haiti's northwest coast and a program to stimulate agriculture production as evidence some progress is being made.

But for some Haitians, at least, promises of a better tomorrow ring hollow after two years of seemingly glacial reconstruction efforts in the poorest country in the Americas.

I stopped living after the quake, said Dieuline Mesidor, a 39-year-old mother who spoke outside the damaged Sacre-Coeur church in the capital.

She said she lost a son and a daughter in the earthquake. I've lost all interest in life, she said.

After paying her tribute to the dead at the main Port-au-Prince cemetery, Marie Michele Edouard told a reporter, I can't shake the image of that day from my mind.

Sometimes I can still hear the wails of people asking for help in my head at night, she said.

(Additional reporting by Swoan Parker; editing by Tom Brown and Mohammad Zargham)