UN chief Ban Ki-moon prepared to visit the quake-struck city of Concepcion yesterday and report on the damage as new fears spread among Chileans following three strong aftershocks.

Rescue workers in the hard-hit coastal city called off their search for the last remaining person, a 26-year-old woman, missing in a 15-story Alto Rio building that toppled in the quake. About 12 people were killed in that building alone, according to the authorities.

The Navy meanwhile sacked the head of the Oceanography Service, saying he had failed to provide a clear warning of the killer tsunami that followed the 8.8-quake a week ago, as criticism grew of the government's disaster response.

Among the three powerful aftershocks that jolted people awake last Friday was a 6.8-magnitude tremor - one of the strongest of more than 200 to rattle Chile in the aftermath of the disaster that has left more than 800 people dead and some two million homeless.

Some damaged buildings in Concepcion collapsed, but the national emergency services said the aftershocks caused no injuries or serious damage.

Oceanography chief Mariano Rojas was removed from his post last Friday, and the head of the Navy said it had opened an investigation into "the decision process after the natural catastrophe".

Military officials have admitted transmitting "very unclear information" to President Michelle Bachelet on whether to lift or maintain a tsunami alert, as giant waves began crashing into the Pacific coast.

Ban, on a visit to Chile to assess damage and bolster aid, pledged $10 million in immediate help from the UN and helped launch a 24-hour telethon on Friday night featuring artists and athletes in a bid raise 15 billion pesos ($29 million) for disaster victims.

Having met with Bachelet and president-elect Sebastian Pinera, Ban was also set to visit the devastated port town of Talcahuano yesterday and meet with the heads of the 22 UN agencies operating in Chile.