The US Geological Survey says an earthquake with a preliminary magnitude of 5.1 has struck northern Pakistan. There have been no initial reports of damage or injuries. The quake struck at 12:23 am (0623 GMT) and was felt in the capital, Islamabad.
The USGS says the epicenter was 48 miles (77 kilometers) east of Mingora, the main city in the Swat Valley in Pakistan's northwest, and 86 miles (138 kilometers) north of Islamabad.
Pakistan's Meteorological Office gave the preliminary magnitude of Monday's quake as 5.2. Magnitudes recorded by different institutes often vary in the initial hours and days after an earthquake strikes.