Gordon Brown has hailed a "strong" show of solidarity from Barack Obama and other G8 leaders in Britain's row with Iran over a detained embassy employee.

The Prime Minister thanked leaders of the powerful nations after they issued a communique demanding that Tehran allow embassies to exercise their functions "without arbitrary restrictions on or intimidation of their staff".

The G8 - made up of Britain, the US, Germany, France, Italy, Canada, Japan and Russia - also warned Iran that arrests of foreign nationals and journalists were "unacceptable" in the wake of the unrest which followed last month's disputed presidential elections.

The communique, agreed over dinner at the end of the first day of the summit in L'Aquila, said: "G8 countries continue to be seriously concerned about recent events in Iran. Interference with the media, unjustified detentions of journalists and recent arrests of foreign nationals are unacceptable.

"Embassies in Iran must be permitted to exercise their functions effectively under the Vienna Convention without arbitrary restrictions on or intimidation of their staff."

The document also voiced concern over Iran's nuclear ambitions, which Tehran insists are limited to civil power, but are widely thought to be directed at developing a weapons capacity. "We remain deeply concerned over proliferation risks posed by Iran's nuclear programme," said the communique. "We strongly urge Iran to co-operate fully with the International Atomic Energy Agency and to comply with the relevant UN Security Council resolutions without further delay."

Mr Brown said: "We pushed for a very strong statement on Iran and this is a strong statement from the whole of the G8. I am grateful for the solidarity of the other leaders."

Meanwhile, thousands of protesters have streamed down streets in Tehran chanting "death to the dictator" and defying security forces who fired tear gas and charged with batons, witnesses said.

The first opposition foray into the streets in nearly two weeks aimed to revive mass demonstrations that were crushed in Iran's post-election turmoil. Iranian authorities had promised tough action to prevent the marches, which supporters of opposition leader Mir Hossein Mousavi have been planning for days through the internet.

Heavy police forces deployed at key points in the city ahead of the marches, and Tehran's governor vowed to "smash" anyone who heeded the demonstration calls.

• 

  Sex, lies and the Stasi

  On this day in 1989 the Berlin Wall was finally breached, ending the reign of East Germany’s feared security service. Here Anne McElvoy, who spent much of the Eighties in the city, recalls her encounters with the spooks

  ---

• 

  The geeky-girl solo artists descending on the music scene

  Kookiness is what sells music these days and these opinionated artists have it in spades, says Jasmine Gardner

  ---

Why Sam's in the clear over that M&S dress

At last the truth about the M&S spotted dress that Sam Cam wore to the Conservative Party Conference

All stories