Talca - Three powerful aftershocks Friday spread new terror among weary Chileans traumatized by a huge quake and tsunami as UN chief Ban Ki-moon was due to arrive to assess the damage.

A first 6.2-magnitude quake jolted people awake at 6:20 am (0920 GMT), just six days after Saturday's record 8.8-quake and ensuing tsunami waves killed over 800 people and left some two million homeless.

That was then followed Friday by a 6.8-magnitude tremor -- one of the most powerful of more than 200 to rattle Chile since the weekend -- followed swiftly by another measuring 6.6.

Buildings in Concepcion, the country's second city, already damaged in the disaster collapsed, although the national emergency services said Friday's quakes caused no injuries or serious damage.

They came as the country prepares for three days of national mourning starting from midnight Sunday, when flags are to be hung on front doors around the nation out of respect for the dead. Related article: Five days after tsunami, food reaches hungry Chileans

In the central city of Talca, 300 kilometers (186 miles) south of the capital, life was slowly returning to normal.

Long queues formed outside banks and automatic tellers were functioning. Many gas stations, supermarkets and shops were open, though many stores were reduced to rubble or remained locked up.

The streets were busy with vehicles and people going about their business, open-air markets were open and phone lines were functioning.

But in the devastated old heart of the city, where street after street of homes crumbled to the ground in the quake, people remained camped in tiny tents or on the streets complaining of government negligence.

"We have not received even a glass of water from the government," said Manuel Carvahaj, 53, busy cobbling together a makeshift center to protect a group of homeless senior citizens from pending rain.

"People have come individually to give us food and water, so has the church, but no official has even come to check on us though we need tents, food, water and toilets."

Outgoing President Michelle Bachelet has predicted it could take up to four years for the South American nation to fully recover from its worst quake in half a century.

"This is testing us as a nation once again. Chile will get back on its feet. What has happened to us is terrible, of colossal dimensions," Bachelet said.

Bachelet said a "simple and austere" handover ceremony will be held next Thursday when president-elect Sebastian Pinera takes up the reins of power. Scene: In southern Chile daily life slowly resumes

Pinera, a multimillionaire rightwing businessman, has pledged that he is reshaping his programs and priorities to focus on the nation's reconstruction which could cost tens of billions of dollars.

The UN secretary general was meanwhile due to arrive in the capital Santiago Friday to assess the damage and meet with Bachelet.

The official death toll stands at 802, but Bachelet said it included some 200 people who should be listed as missing but were prematurely added to the death toll.

Thousands of Chilean troops sent to central and southern regions have largely managed to quell the looting that erupted in the wake of the disaster.

Bachelet has deployed 14,000 troops and imposed broad curfews in the quake region, an unprecedented move since the 17-year military dictatorship of Augusto Pinochet which ended in 1990.

The cheers and plaudits greeting Chilean soldiers along the country's tsunami-flattened coast point to a long march by the army since the days of Pinochet's repressive military regime.

"The army has been fabulous," said 69-year-old retired teacher Osvaldo Fuentes in Constitucion after lifting water from a military truck. "Everyone is applauding them."

"I think people are extremely happy to see the support the army is offering in this crisis," General Bosco Pesse, the chief of emergency operations in the disaster zone, told AFP.

Despite being considered a model of political and economic stability in Latin America, Chile has struggled to cope with a catastrophe of this scale, with many of the nation's lifeline industries decimated by the disaster.