A British man has been killed and four others injured after they were attacked by two Greek taxi drivers on the holiday island of Zakynthos.
The Foreign and Commonwealth Office (FCO) has confirmed they are assisting the families of the victims.
The attack took place early today at the popular Lagana resort, where the two Greek drivers have been arrested and detained, local police said.
The four injured Britons are being treated in hospital for injuries that are not life-threatening.
One Greek news website said the dead man was aged 19 and had been with friends outside a nightclub when the argument started with the taxi drivers.
Another website reported that one of the offenders said after the incident: "I was annoyed because the young British tourists bothered us with lasers."
An FCO spokeswoman said: "We can confirm that five British nationals were involved in a serious incident in Zakynthos, Greece.
"Sadly, this resulted in the death of one British national and the hospitalisation of four others, one in a serious condition.
"We are in regular contact with the families of those involved and are providing consular assistance."
The two taxi driver suspects are due to appear before a magistrate on the Greek island later.
The 21-year-old is facing a murder charge while his 25-year-old colleague is charged with complicity to commit murder.
Reports have said the incident followed a laser pen being aimed at the drivers.
A local police spokesman said: "The two Greek taxi drivers were involved in an argument with a group of six foreign nationals, resulting in a physical confrontation.
"A 21-year-old taxi driver attacked and injured five British nationals, one of whom suffered fatal injuries,"
The knife allegedly used by the 21-year-old suspect has been recovered at a coastal area near the main town of Zakynthos.
The western Greek island of Zakynthos, also known as Zante, is a popular destination for Britons, with direct charter flight links to several cities.