In Tehran today, Iranian officials claimed to have confessions from 15 captured British Royal Navy personnel -- eight sailors and seven Marines, reportedly including one woman -- who were taken at gunpoint by armed Iranians.
The British forces had been searching a large cargo dhow (wooden merchant ship) that they suspected of smuggling in the northern Persian Gulf.
Mark Fitzpatrick, a former U.S. diplomat and currently a senior fellow at the International Institute for Strategic Studies in London, told ABC News: "I think it's clear that the Iranian Navy has orders to detain anyone who crosses their line."
Fitzpatrick thinks the situation is not one that was meditated by either side in order to cause a crisis.
Fitzpatrick himself did not claim to know whether British forces had cross the line, but told ABC News, "I was at a reception last night where the Iranian Chargé D'affaires said that this was the case, and that Iranians believed they had crossed the line."
In Tehran, Iranian officials turned up the heat with the 'British confession' claim. Gen. Ali Reza Afshar, deputy to the chief of Iran's military staff said: "British marines, who were arrested by the Navy force of the Iranian Revolutionary Guard, have confessed that they knew that they were in Iranian territorial waters."
The Iranian general added, "This is not a new thing, and British forces have violated Iran's territorial waters during their Iraq occupation. We had warned them before but they did not pay any attention. They should know that Iran is strong enough to defend itself and its territorial integrity."
"They [The Iranian leadership] are always playing to a domestic audience," said Fitzpatrick of the IISS. "They're trying to justify to their domestic audience, and to the world, why they detained the sailors, and saying that they confessed."
Despite the heated rhetoric from Tehran, diplomatic discussions resumed in London today. The one-hour session between British Foreign Office Minister David Triesman and Iranian Ambassador Rasoul Movahedian was described by British officials as "frank and civil," and aimed at seeking assurances that the group was unharmed and would be seen by diplomats in Tehran.
Previous statements out of Tehran have claimed that the sailors and Marines are safe.
Yesterday, British Foreign Secretary Margaret Beckett issued this statement: "We sought a full explanation of what happened, and left the Iranian authorities in no doubt that we expect the immediate and safe return of our service personnel and boats."
The U.S. 5th Fleet, which operates with British forces off Iraq and monitors activity in the area, said the capture was carried out by Iranian Revolutionary Guard naval forces off the disputed Shatt al-Arab waterway that divides Iran and Iraq.
British Commodore Nick Lambert of the HMS Cornwall, where the sailors and marines had been based in the Persian Gulf, said: "There is absolutely no doubt in my mind that they were in Iraqi territorial waters."
But he added, "Equally, the Iranians may well claim that they were in Iranian territorial waters. The extent and the definition of territorial waters in this part of the world is very complicated. That is one of the reasons we're here."
The Shatt al-Arab waterway, where the group was intercepted, divides Iran from Iraq and is an important water route for valuable oil supplies. The disputed territory and the lands around it were the focus of the Iran-Iraq war, which lasted from 1980 to 1988 and claimed the lives of more than one million people.
It is not the first boat crisis between Iran and Britain. In a similar incident three years ago, eight British sailors and marines were captured by Iran inside the Shatt al-Arab, and later released. At that time, Iran also claimed that it's territory had been invaded. Britain said it had been inside Iraqi waters, and repeated that position immediately after this latest incident.
"I think there is always a possibility where a situation like this could be exaggerated and taken out of control," said Fitzpatrick. "I don't think it's going to happen this time. I think the Iranians, I hope the Iranians, are wise enough to realize they can not hold on to these sailors and marines for much longer.
"The United Kingdom and the United States are not going to just stand still while their men and women are detained by Iran," he added. "I don't see the United Kingdom standing for that very long. And there are ways in which they could escalate it. And there is no point for Iran to do this."
However, it is currently the middle of an Iranian New Year's holiday period, so it could be days before high-ranking Iranian officials come to grips with this latest explosive incident in the Gulf.