The two, who are siblings from Dublin, have had their passports confiscated after their involvement in the row in the Sea Casino restaurant, which resulted in the owner of the premises, Mariyan Milanov, being rushed into emergency surgery in hospital with three stab wounds to the stomach. His condition has been described by doctors as stable.

The siblings were with a group of around 15 Irish tourists who were in the restaurant earlier this week.

The fight erupted when staff refused to serve drinks after closing time.

It is believed that an Irishman who was with the group was also stabbed. A number of Irish tourists are being questioned by Bulgarian police. It is understood they were staying in the Bravo Hotel in the Sunny Beach resort.