A strong 6.1 magnitude earthquake and at least three aftershocks shook northwestern Nicaragua on Thursday night, triggering panic among residents.

There were no immediate reports of damage or casualties.

The 6.1 quake struck at 9:25 pm (0325 GMT), centered 17 kilometers (10.5 miles) east of Puerto Morazan near the Honduras border at a depth of 10 kilometers, according to the United States Geological Survey.

It was followed by three weaker aftershocks within the next 20 minutes, USGS said.

"The quake was felt almost throughout the country," government spokeswoman and First Lady Rosario Murillo said, calling it "unusually strong."

She urged residents to stay calm, warning of the threat of more aftershocks.

Puerto Morazan is about 125 kilometers northwest of the capital Managua.