Journalists and guests at the inauguration of Sebastian Pinera as Chile's new president react to an aftershock a few minutes before the start of the ceremony in Valparaiso on Thursday. (Ivan Alvarado/Reuters)A series of powerful aftershocks hit Chile on Thursday just 12 days after February's massive earthquake and minutes before the new president, Sebastian Pinera, was sworn in.

The U.S. Geological Survey said the second in a series of seven aftershocks was a magnitude 6.9. It struck about 125 kilometres west-southwest of Santiago and was measured at a depth of 10 kilometres. The USGS initially estimated the aftershock at 7.2.

Chile's navy issued a tsunami warning after the aftershocks shook the region. There were no immediate reports of damages or injuries.

The aftershocks were a reminder of the 8.8-magnitude quake that struck Chile on Feb. 27 just off the coast, which caused buildings to collapse and triggered a tsunami that battered the country's coastline. About 500,000 homes were destroyed and hundreds of people were killed.

The aftershocks came as Pinera's inauguration ceremony was about to get underway in the coastal city of Valparaiso, about 120 kilometres west of Santiago.

A map of aftershocks to hit Chile since the magnitude 8.8 earthquake struck on Feb. 27. Larger circles represent stronger tremors. (USGS)

The event attracted dignitaries from around the world, including Peter Kent, the Canadian minister of state of foreign affairs for the Americas. Bolivian President Evo Morales seemed briefly disoriented when the aftershocks struck. President Alan Garcia of Peru joked that it gave them "a moment to dance."

Pinera entered the hall of Congress to loud applause, shaking hands with politicians and dignitaries before swearing his oath as president.

He then urged coastal residents to move to higher ground and had the hall of Congress, which itself lies close to the coastline, evacuated.

Pinera, who succeeds Michelle Bachelet, has vowed to spend billions on reconstruction efforts and accelerate economic growth.

Chile has estimated that repairing infrastructure alone after the disaster would cost $5 billion US, and that overall recovery costs could soar above $15 billion US.

With files from The Associated Press