Santiago, Chile (CNN) -- Three strong earthquakes rocked Chile on Thursday, causing significant damage in at least one city, the country's newly inaugurated president said Thursday.
A 6.9-magnitude earthquake hit at 11:39 a.m. local time (9:39 a.m. ET), followed by a 6.7-magnitude quake 16 minutes later, the U.S. Geological Survey reported. A third, measured at magnitude 6.0, came 27 minutes later.
They were the strongest aftershocks to rattle Chile since a February 27 earthquake on the country's west coast that toppled buildings and spawned a tsunami, killing several hundred people.
Thursday's quakes shook the ground near Libertador General Bernardo O'Higgins near the coast just as Chile prepared to inaugurate a new president, Sebastian Pinera.
The central Chilean city of Rancagua was affected, Pinera said.
"There is significant damage in Rancagua," the new president said. "We're going to send the necessary armed forces to guarantee citizens' safety."
Rancagua Mayor Eduardo Soto said that no fatalities were immediately reported and that the biggest worry was damage to homes, CNN Chile reported.
After his inauguration Thursday, Pinera visited Rancagua, where he confirmed there were no initial reports of fatalities.
He said that no curfew would be imposed for now and reiterated his call for calm. A priority is for the school year to start as scheduled next week, he said.
He also said Thursday afternoon that he would declare the area a catastrophe zone.
The country's national emergency authorities also put in place a tsunami alert for the coastal area near where the earthquakes hit, and authorities ordered evacuations of some coastal areas.
"I don't want to alarm anyone, [the alert] is solely precautionary, but we have to take precautions when there are human lives at risk," Pinera said.
The epicenter of Thursday's first quake was about 95 miles (152 km) south-southwest of the capital, Santiago, and about 90 miles (145 km) away from Valparaiso, where Pinera was to be inaugurated. Television footage showed the inauguration proceeding without a hitch.
A second earthquake -- with an initial magnitude of 6.9 -- struck moments later. It was about 89 miles (143 km) southwest of Santiago, the USGS said. The third was about 86 miles (138 km) southwest of Santiago.
Rolando Santos, senior vice president and general manager of CNN Chile, said he and his colleagues felt one of the quakes.
"I can tell you within our newsroom in Santiago, which is state of the art in terms of seismic construction, it shook for more than 45 seconds," he said.
He said that he told staffers to get under desks and that three people burst into tears. In the last two days, people had kind of gotten used to aftershocks, but "there was no question this one got everyone's attention," he said.
Pinera, a conservative billionaire businessman, became the Chilean president about 12:15 p.m. local time, roughly 20 minutes after the second quake.
The Pacific Tsunami Warning Center said in a statement that "a destructive Pacific-wide tsunami is not expected" as a result of the quakes, and that there is no tsunami threat to Hawaii.
However, the center also said that "earthquakes of this size sometimes generate local tsunamis that can be destructive along coasts located within" about 62 miles (100 km) of the epicenter.
Hundreds of people were killed when the magnitude-8.8 earthquake struck Chile's west coast February 27. That quake also triggered a tsunami that toppled buildings, especially in the coastal Maule region.
Authorities this week released the names of 279 people whose bodies had been identified in the quake, but officials said the new tally does not include hundreds of unidentified victims.
The February 27 earthquake was violent enough to move the Chilean city of Concepcion at least 10 feet to the west and Santiago about 11 inches to the west-southwest, researchers said.