Survivors of the strongest typhoon ever to hit land wept at mass graves on Saturday during ceremonies to mark one year since the storm devastated the central Philippines and condemned millions to deeper poverty.

Super Typhoon Haiyan claimed more than 7,350 lives as it swept in off the Pacific Ocean, with its record winds and once-in-a-generation storm surges flattening entire towns.

The typhoon tore across a corridor of islands where about 14 million people lived in farming and fishing communities that were already among the nation's poorest.

The rebuilding effort has been painfully slow for most survivors, with millions poorer and many dangerously exposed to the next big storm as they still live in shanty homes along coastal areas.

In an outpouring of grief, thousands marched to mass grave sites scattered across the typhoon zone on Saturday to offer flowers, light candles and say prayers.

Josephine Crisostomo, 41, whose three children died during the storm, was among a big crowd at a site on the outskirts of badly hit Tacloban city where more than 2,000 people were buried.

"I miss my children terribly, especially John Dave who would have celebrated his birthday tomorrow... I miss you, son, I love you so much," Crisostomo said.

Using felt-tip pens, mourners wrote names of those who died on the hundreds of white crosses planted on parched earth in symbolic gestures as many of those buried there had not been identified.

"I am looking for my brother, but his name is not on the list of those buried here," Elena Olendan, 50, told AFP, her eyes welling with tears, as she wandered around the grave site, about the size of six basketball courts.

Olendan then found a cross at the far end of the mass grave and wrote her brother's name, Antonio, on it.

The Philippines is a mainly Catholic country and many people in the typhoon zones, as well as across the nation, attended special church services.

At the Tacloban grave site, white doves and balloons were released after a bishop gave a mass.

Tacloban city mayor Alfred Romualdez, who attended the ceremony, said Saturday's solemn rites gave the survivors an opportunity to let emotions come out.

"It's bittersweet because while they survived, they lost their loved ones, their livelihood and their homes. Now is really the time for them to grieve," Romualdez told AFP.

- Slow pace -

The build-up to the anniversary had focused renewed attention on the pace of the reconstruction effort, with President Benigno Aquino's government criticised by many for a perceived lack of urgency.

Roughly one million people need to be moved away from coastal areas that are deemed vulnerable to storm surges, according to a 160-billion-peso ($3.6-billion) government master plan for rebuilding the typhoon zones.

However those plans have already fallen behind schedule, delayed by problems in finding new land that is safe and suitable for 205,000 new homes.

Across the typhoon-hit islands, schools, health centres, gymnasiums and other important community buildings are also yet to be rebuilt or repaired.

In a speech at the typhoon-hit town of Guiuan on Friday, Aquino defended the pace of the reconstruction and recovery programme, saying he was determined to ensure it was carried out correctly rather than rushing.

"Curse me, criticise me but I believe I must do the right thing," Aquino said.

"I am impatient like everyone else but I have to stress that we can't rebuild haphazardly. We have to build back better... let's get it right the first time and the benefits should be permanent."

And while millions are enduring Haiyan-exacerbated poverty, there has been some remarkable progress from a year ago, partly due to international aid agencies pumping hundreds of millions of dollars into the region.

Some of the big successes of the campaign have been the restoration of electricity within a few months, quick replanting of rice crops and sanitation programmes that prevented major outbreaks of killer diseases.

Tacloban, home to 240,000 people, again resembles many other chaotic Philippine cities, with traffic jams, busy market stalls and packed shopping malls.