Spectators observe a national minute's silence for victim's of the attacks in Tunisia a week ago at the Wimbledon Tennis Championships in London, July 3, 2015.[Photo/Agencies]

LONDON - Millions of people across Britain held a minute's silence on Friday on an official day of mourning to pay tribute to 30 Britons killed a week ago by an Islamist gunman in Tunisia, the country's worst loss of life in a militant attack in a decade.

The Britons were among 38 killed when Saif Rezgui opened fire on holidaymakers at the resort of Sousse in the North African country.

Flags on government buildings, UK embassies around the world and at Buckingham Palace in London flew at half mast while at airports, train stations and across the country, millions of Britons, including Queen Elizabeth and Prime Minister David Cameron, fell silent at midday in memory of those killed.

Organisers at the Wimbledon tennis tournament delayed the start of play to allow spectators and those in the grounds to pay their respects, while other sporting events including the British Grand Prix were also marking the day.

In Tunisia, the British Embassy was planning to hold a memorial ceremony and lay wreaths on the beach where the attack took place.

Last Friday's attack saw the highest number of Britons killed in a militant incident since four young British Muslims carried out suicide bomb attacks on London's transport network on July 7, 2005, killing themselves and 52 others.