Tens of thousands of Chinese have flooded the streets of one of the towns hardest hit by last year's Sichuan earthquake to mark the anniversary of the disaster.

One year ago, Beichuan was reduced to rubble in the 8.0-magnitude quake in southwestern Sichuan province, one of the worst natural disasters in China's history.

In total, the quake left 87,000 people dead or missing, at least 20,000 of those in Beichuan.

'I came here to mourn for the children who died at the school,' said Han Jianmin, an office worker from the nearby city of Mianyang, which also suffered significant damage in the quake.

'The school house collapses were the most tragic part,' she said as she burned piles of paper money - offerings to the dead children - near the ruins of Beichuan Middle School.

Like many here, Han and her group of friends did not suffer any immediate family losses in the tragedy, but knew several people who lost their lives.

Due to the vast destruction in Beichuan, the county seat, the town has largely been kept off limits to the public, but was reopened to the public for four days from Sunday to allow people to mourn.

Roads to the mountainous town have been jammed with vehicles as survivors and tourists alike come to remember those lost.

'I have come to mourn the loss of my two brothers and their wives,' said 46-year-old Wu Guangjun.

'They are still in the rubble. We have not found their bodies.'

Wu, a short and stocky migrant construction worker, was not home at the time of the disaster - a stroke of luck as by his own account, he would almost certainly have been among the dead here had he stayed.

Mourners wept as they knelt before collapsed buildings and set off firecrackers to ward off evil spirits. Many lit incense and burned paper money.

Police say it is hard to calculate how many people are in Beichuan for the anniversary, but one official estimates that up to 100,000 people have arrived at the town that is to be preserved as an earthquake museum.

Stalls and shops line the road outside the gate of Beichuan, with vendors selling earthquake souvenirs, ethnic Qiang minority arts and crafts and local specialties such as wild mushrooms, fruits and nuts.

The government has told locals that tourism could help them recover from the tragedy that has left millions homeless and out of work.

'I'm commemorating the anniversary of the earthquake by transporting people,' said a local motorcycle taxi driver surnamed Zeng.

'The earthquake has left many here destitute, we need to eat, but we do not have much money,' he said, thanking one tourist for a generous tip.

'Since the earthquake, this is the most people I have seen here at one time,' said a Beichuan farmer surnamed Wang who was doing a brisk business selling snacks at the town's gate.

'A lot of locals did not like the idea of turning Beichuan into an earthquake museum because this tragedy has been very personal,' she said.

Amid all the attention however, some survivors are just hoping for peace and quiet.

'I am 89 years old and I have never experienced anything like the quake. My house was completely destroyed, I lost everything I had,' said Yuan Chuanzhen from her new home, a Red Cross-funded nursing facility in Mianzhu.

'I'm lucky, all eight of my children survived. Now they must look for jobs, so they can't take care of me. That's why I came here.'