Haiti's President Rene Preval has vowed that his country will live on.
"Haiti will not die, Haiti must not die," he told mourners at the main service in Port-au-Prince. "Wipe away your tears to rebuild Haiti.
"Today, allow me as citizen Rene Preval, the man, the father of a family, to address you to say that I cannot find the words to speak of this immense pain.
"It is in your courage that we will find the strength to go on."
Other prayer services were held across the country, including one at the site of a mass grave north of the capital, in Titanyen, which is believed to hold tens of thousands of victims.
The BBC's Mike Wooldridge says the act of national reflection comes as one of the largest humanitarian operations ever mounted grapples with challenges on many fronts.
He says a heavy downpour on the eve of the commemoration provided a foretaste of the misery that lies ahead for the many people who still have only the flimsiest shelter in impromptu camps, if the pace of getting out more tents and stronger shelter materials is not stepped up before the start of the rainy season.
AT THE SCENE
By Mike Wooldridge, BBC News, Titanyen
Amid scrub-covered hills to the north of Port-au-Prince, some 50 worshippers led by a Haitian bishop celebrated Mass on the graves where tens of thousands of the earthquake victims lie buried.
A small wooden table atop one of the mass graves in the scrub-covered low hills served as the altar.
Swinging incense above the graves and sprinkling water on them, the bishop said he aimed to give dignity to their hasty burial.
"Tend to your brothers and sisters, calling out from under the ground," he said.
In the biggest of the camps that sprang up in the capital after the earthquake, people are still living under sheeting strung across wooden poles.
The government says the seasonal rains could be the biggest threat now to the nation's attempts at recovery.
The European Union has proposed a military mission to step up the provision of shelter before the rains worsen.
The UN aid co-ordinator for Haiti, former-US President Bill Clinton, said Haiti could get through the crisis with the help of international donors.
"Though conditions are improving each day, countless people remain in urgent need of shelter and building materials, water and sanitation, food and clothing, and essential medical supplies," he said in a statement.
The White House warned that the situation in Haiti "remains dire", but added that the US "continues to stand with our Haitian friends as they recover".
This week's Haitian government figures suggesting up to 230,000 dead means the quake toll is approaching that of the 2004 Asian tsunami, which killed 250,000 people.
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