Two young men, one 15 and the other 16, were stabbed on Saturday afternoon following a feud at in Estoril near Lisbon.
Videos and images show dozens of young men seeming to rush each other at Tamariz beach just after 6pm on Saturday evening.
The video, which has circulated online but is too graphic to show here, shows men of African origin in two rows who then suddenly fight each other with knives in front of horrified tourists and locals relaxing in their deck chairs.
Women and children go running away from the violence with some children being so young they need to be carried away from the danger.
The two young men who were stabbed, it is unclear whether they were part of the gang fight but both are said to be residents of nearby Cascais and both were taken to hospital where they are recovering.
Portuguese police are yet to make a statement and no arrests have been made as of yet.
Stabbings have been rife in Portugal this year with a 40 year old British woman being stabbed 14 times in the back after she returned home with a 22 year old man she met in a bar whilst celebrating her birthday in Albufeira.
The woman from Liverpool, who survived, is reported to have had her drink spiked.
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