Britain's Queen Elizabeth II and Prime Minister David Cameron led a nationwide minute's silence on Friday, a week after a militant gun massacre in Tunisia in which 30 out of the 38 victims were Britons.

Flags flew at half-mast as schools, government offices and the Wimbledon tennis tournament fell silent at midday to honour the victims of Britain's worst terror attack since the 2005 London bombings.

Employees of travel group TUI, which includes operators Thomson and First Choice that organised the holidays of all of the British victims, stood in silence outside the company's headquarters.

There was also a ceremony outside Walsall football stadium in central England in tribute to three local men from the same family who died in the tragedy.

The moment of remembrance for the attack claimed by the Islamic State group comes a day after the British government raised the possibility of extending air strikes against IS militant from Iraq to Syria.

The queen and her husband Prince Philip joined in the silence during a visit to Strathclyde University in Glasgow, while Cameron marked the moment in his Witney constituency northwest of London.

The profile picture on the prime minister's Twitter account was changed to a sign reading "Remember Tunisia" with the first word written in red.

Britain has launched an investigation into the killings and the police said that they had so far taken 275 witness accounts and that more than 1,200 potential witnesses had returned to Britain.

A special ceremony was also held at the scene of the killings on a sunny beach near Sousse, with dozens of officials and tourists in attendance as Tunisia stepped up security at its holiday resorts.

Wimbledon joins in mourning

The killings were the worst-ever massacre in Tunisia, which fears massive damage to its tourism industry.

The sector accounts for about seven percent of gross domestic product in a country already suffering from the upheaval that followed the 2011 overthrow of dictator Zine El Abidine Ben Ali.

St Paul's Cathedral joined in the remembrance and the Muslim Council of Britain also urged imams to deliver a sermon of peace at Friday prayers.

At Wimbledon, the start of matches was delayed by 45 minutes to 12:15pm (1115 GMT) to allow spectators and tennis players to take part.

The bodies of 17 of the British victims have now been repatriated on a military transport plane to Royal Air Force base Brize Norton.

Eight more were due to be brought back to Britain later on Friday and the final five will return on Saturday.

The remains will be released to the families following post-mortem examinations.

Inquests into each of the 30 deaths will be opened to probe the circumstances of each death.

Three Irish nationals, two Germans, one Belgian, one Portuguese and one Russian were also among the dead.

The attack also comes as Britain prepares to commemorate the 10th anniversary of the July 7, 2005 attacks in which four suicide bombers killed 52 people on London's transport network.

Tunisia on Thursday said eight people had been arrested in connection with the massacre by 23-year-old student Seifeddine Rezgui, who gunned down foreign tourists after pulling a Kalashnikov assault rifle from a beach umbrella.

Friday's attack was the second on tourists in Tunisia claimed by IS in three months, after the extremist group said it was behind a March attack on the National Bardo Museum in Tunis that killed 22 people.

Tunisian authorities have said Rezgui received weapons training from militants in neighbouring Libya, travelling to the chaos-wracked country at the same time as the two young Tunisians behind the Bardo attack.

In the past four years, dozens of police and soldiers have been killed in Tunisia in clashes and ambushes attributed to militants -- mainly in the western Chaambi Mountains.

Disillusionment and social exclusion have fuelled radicalism among young Tunisians, with the country exporting some 3,000 jihadist fighters to Iraq, Syria and Libya.