According to the note of the Portuguese Institute of Sea and Atmosphere (IPMA), the event happened at 14:44 and was recorded in the stations of the Seismic Network of the mainland.
The earthquake with epicentre 35 kilometres from Cape Finisterre, in the province of La Coruña, Spain, "was felt with maximum intensity III" on the modified Mercalli scale, in the municipality of Santo Tirso, Porto.
It was also felt, although with less intensity, in the municipalities of Póvoa de Lanhoso, in Braga, and Ponte de Lima, in Viana do Castelo.
The IPMA said that "if the situation warrants, new communications will be issued".
An earthquake with a magnitude between 4.0 and 4.9 on the Richter scale is considered "weak", and unlikely to cause damage.
The Modified Mercalli Scale measures the "degrees of intensity and their description". A level III on this scale refers to a "weak" event, which can be "felt indoors", and its "vibration is similar to that caused by the passage of heavy vehicles", reads the IPMA website.