Twelve strong earthquakes shook Chile Thursday, including some just minutes before the start of the inaugural ceremony of incoming President Sebastian Pinera.

The tremblors - measuring 4.9 to 6.9 on the Richter scale - caused panic in several areas across central-southern Chile, which was hit by a devastating 8.8-magnitude quake Feb 27. Last month's quake and a subsequent tsunami claimed hundreds of lives.

The Chilean Navy issued a tsunami warning, and many in coastal areas fled to higher areas. Thousands of people across the country poured onto the streets in panic, but there were no immediate reports of damage or casualties.

'It is just a warning,' Pinera stressed.

In some areas, the power supply and the telephone network broke down.

The inaugural ceremony at the Congress building in Valparaiso went on as planned. Guests looked nervously at the ceiling as large lamps shook, and bodyguards rushed Spain's Crown Prince Felipe out once the event was over.

Hundreds of strong aftershocks have rattled the South American country since the initial quake last month.

The epicentre of Thursday's strongest such aftershock was around 145 km south of Santiago, and 105 km west of the town of Rancagua. The US Geological Survey initially measured its magnitude at 7.2, but later revised the figure to 6.9.

Pinera, 60, is succeeding outgoing President Michelle Bachelet, who is set to leave office with record popularity. She has the support of 84 percent of Chileans in the quake's aftermath even as members of her government have come under criticism for their handling of the disaster, according to an opinion poll that was made public Wednesday. The head of Chile's National Emergency Office stepped down Wednesday.