Britain said yesterday it was in direct communication with Iran as it seeks the release of 15 detained sailors and marines, while protesters in Tehran hurled stones and firecrackers at the British embassy.
Witnesses heard several small blasts and saw smoke rising from inside the British embassy compound in central Tehran during a protest over 15 detained sailors and marines, but no one was hurt.
One witness cited eight blasts saying they came from small, home-made explosive devices. Britain said no damage had been done and no one was hurt in the incident. The witness also said the blasts did not appear to do any damage, but each one sent a small plume of smoke into the air.
The blasts occurred as demonstrators surged towards a barrier around the Embassy where police were standing. About 200 demonstrators chanted: "British, British, death to you, death to you" at Britain's embassy.
Demonstrators, who scuffled with police, included members of the Basij, a hardline religious militia.
Meanwhile Iranian television said it would show pictures of two British sailors admitting they were in Iranian waters when they were captured on March 23. Footage of a sailor apologising for entering Iranian waters was broadcast on Friday.
Iran's capture of the sailors and marines has drawn international criticism. Tehran has ignored calls to release the 14 men and one woman, saying Britain must admit they illegally entered Iranian waters.
Britain insists they were in Iraqi territory when seized.
The row, at a time of heightened Middle East tensions over Tehran's disputed nuclear programme, pushed oil prices last week to six-month highs. The West accuses Iran of trying to build nuclear bombs, a charge Tehran denies.
British Defence Secretary Des Browne said diplomatic efforts were continuing to resolve the crisis.
"We are anxious that this matter be resolved as quickly as possible and that it be resolved by diplomatic means and we are bending every single effort to that," Mr Browne told BBC television.
"It's not my intention to go through the detail of that blow by blow, and it wouldn't be appropriate to do that, but we are in direct bilateral communication with the Iranians," he said.
US President George W. Bush on Saturday called on Iran to release the 15 at once. "The Iranians must give back the hostages. They're innocent," he said. "The Iranians took these people out of Iraqi waters. It's inexcusable behaviour."
Mr Bush's use of the term "hostages" evoked the storming of the US embassy in Tehran after the 1979 Islamic revolution and the holding of 52 Americans for 444 days. Washington broke off relations as a result.
Responding to Mr Bush's comments, Iranian Foreign Ministry spokesman Mohammad Ali Hosseini said the US could damage the British cause, the Iranian state TV website said.