The British government said it was in direct contact with Iran and examining options for new dialogue over the seized crew of 15 sailors and marines. There were few signs of tensions easing in Iran, where students pelted Britain's embassy with rocks and firecrackers and a television station aired new footage of two captured seamen in front of a map of the Persian Gulf.
Defense Secretary Des Browne said on Sunday that Britain was in "direct, bilateral communication with the Iranians." A Ministry of Defense spokeswoman said Browne was referring to letters and other contacts between diplomats, rather than any new face-to-face talks.
Browne, on a visit to Afghanistan, said Britain had "the support of almost the whole international community" in calling for the release of its personnel, who were seized by Iran 10 days ago.
Transport Secretary Douglas Alexander said Britain was engaged in "exploring the potential for dialogue" with the Iranians. Officials were holding a crisis committee meeting to discuss developments.
"The responsible way forward is to continue the often unglamorous, but important and quiet diplomatic work to get our personnel home," Alexander told the British Broadcasting Corp.
Government and defense officials refused to discuss a newspaper report that claimed a Royal Navy captain or commodore would be sent to Tehran as a special envoy to negotiate a release of the crew.
The Sunday Telegraph newspaper reported that the naval envoy would deliver an assurance that British naval crews would never deliberately enter Iranian waters without permission.
The eight British sailors and seven marines were detained on March 23 by Iranian naval units while patrolling for smugglers near the mouth of the Shatt al-Arab, a waterway that has long been a disputed dividing line between Iraq and Iran. Tehran says the crew was in Iranian waters, but Britain insists its troops were on the Iraqi side of the maritime border.
New footage of two mariners was broadcast Sunday on Iranian state-run television channels. Two Farsi-language Islamic Republic of Iran Broadcasting channels showed the two sailors, who wore military fatigues and appeared relaxed, in separate video clips. Both sailors pointed at the same map of the Persian Gulf.
The first sailor, who was identified as Royal Marine Capt. Chris Air, pointed with a pen to a location on the map where he said two boats left a warship of the U.S-led coalition in Iraq around 8:30 a.m. on March 23. He said the seven marines and eight navy sailors were captured around 10 a.m.
Pointing to the map, he said "we were seized apparently at this point here on their maps and on the GPS they've shown us, which is inside Iranian territorial waters."
"And so far we have been treated very well by all the people here. They have looked after us and made sure there's been enough food and we've been treated very well by them so we thank them for that."
The second sailor, identified as Lt. Felix Carman, pointed to an area on the map and said that location was where he and the 14 others were arrested.
"I'd like to say to the Iranian people, I can understand why you are so angry about our intrusion into your waters," he said.
The newscaster said the two had confessed to "illegally" trespassing in Iranian waters.
Iran's official Arabic-language TV station, Al-Alam, also showed the video clips but initially aired them without the soldiers' voices. Several hours later, it also aired the clips with the soldiers speaking in English.
The Foreign Office condemned the video, saying it was "completely unacceptable for these pictures to be shown on TV."
In Tehran, about 200 students threw rocks and firecrackers at the British Embassy, calling for the expulsion of ambassador Geoffrey Adams.
The protesters chanted "death to Britain" and "death to America" as they hurled stones into the embassy's courtyard. Britain's Foreign Office said nobody was hurt and there had been no damage to the compound.
In London, about a handful of demonstrators protested outside the Iranian Embassy, waving placards saying "Let them go, Iran" and "Honk for the hostages."
A Defense Ministry spokeswoman declined to comment on claims British authorities had lost hope in a quick resolution to the standoff, saying speculation about diplomatic efforts threatened to hinder progress.
Former Foreign Secretary Malcolm Rifkind, of the main opposition Conservative party, said Sunday that "rhetoric by itself will not deliver freedom for these people."
He called for European Union allies to support Britain if it chose to threaten future sanctions against Tehran, including the withholding of export credit guarantees for companies doing business in Iran.
"You need pressure," Rifkind told the BBC.
The threat of sanctions could "quietly and successfully" put pressure on Iran to free the crew, Rifkind said.
The European Union, Iran's biggest trading partner, has demanded the captives' release but is cool to the idea of economic sanctions.
"Britain enjoys the full solidarity of the European Union on this issue," German Chancellor Angela Merkel said Sunday during a visit to Israel. "We demand the immediate release of the 15 British soldiers."
U.S. President George W. Bush on Saturday called for the crew's release, labeling its capture by Tehran "inexcusable behavior" and referring to the captured Britons as "hostages" - a word avoided by British officials.
Iranian President Mahmoud Ahmadinejad insisted the Britons had trespassed in Iranian waters and called world powers "arrogant" for failing to apologize.
The Muslim Council of Britain, the country's largest Islamic umbrella group, said it had written the Iranian ambassador in London asking that the sailors and marines be released on humanitarian grounds.