A moderate 5.4-magnitude earthquake has struck the Atlantic Ocean off Portugal, making it the strongest earthquake in the region in 15 years, according to seismologists, Paralel.Az reports citing BNO News.

Shaking was felt in Lisbon and as far away as Morocco.

The earthquake, which struck at 5:11 a.m. local time on Monday, was centered in the ocean about 64 kilometers (40 miles) southwest of Sesimbra, or 85 kilometers (53 miles) southwest of the capital city.

The U.S. Geological Survey (USGS) said Monday’s tremor had a magnitude of 5.4 and struck about 17 kilometers (10 miles) below the seabed, making it a shallow earthquake. Portugal’s seismological agency, IPMA, put the magnitude at 5.3.

Shaking was felt across the region, including in Lisbon and other nearby cities where scores of people said the tremors were strong enough to wake them.