Britain, which failed to win strong UN Security Council condemnation of Iran over the detention of its 15 sailors and marines, vowed it would work to further isolate the Islamic republic over the crisis.

Prime Minister Tony Blair voiced his "disgust" at the latest broadcast of the captive Britons and Foreign Secretary Margaret Beckett said she saw no sign that Iran was seeking to solve the crisis.

"We've got to pursue this with the necessary firmness and determination but also patience," Blair said. "The most important thing is to make sure that our people are returned safe."

But Tehran has so far refused to bow to mounting international pressure to release the 14 men and one woman seized in the northern Gulf a week ago and now being held in a secret location.

Britain insists they were on a routine anti-smuggling patrol in Iraqi waters but Iran says they were in its territorial waters.

"I would like to apologise for entering your waters without any permission," the Royal Navy serviceman identified as Nathan Thomas Sommers said in an interview broadcast on Arabic-language Al-Alam television.

"Since we have been arrested in Iran our treatment has been very friendly, they took care of us very well."

The interview was interspersed with images of the sailor sitting with two of his captured colleagues, including the only woman Faye Turney, smiling, and with bowls of fruit and flowers in front of them.

In the first footage of the group aired on Wednesday, Turney was also shown saying that they had trespassed into Iranian waters.

"Using our military personnel for purposes of propaganda like this is outrageous," Britain's Foreign Office said.

Britain has already frozen most ties with Iran, a move Tehran blamed for its decision not to free Turney as promised earlier this week.

The Security Council on Thursday expressed "grave concern" at Iran's detention of the 15 although it failed to back Britain's demands for a stronger statement and demand their immediate release.

The affair has dramatically increased tensions between the Islamic republic and the West, which are already at loggerheads over Iran's disputed nuclear programme.

The Britons were seized a day before the Security Council adopted tough new sanctions on Iran for failing to freeze uranium enrichment, a process at the centre of fears Tehran might be secretly trying to build atomic weapons.

The crisis has sent oil prices surging towards seven month highs, topping 69 dollars in London trade on Friday.

Ankara has been trying to mediate in the crisis, but on Friday Iranian President Ahmadinejad was quoted as telling Turkish Prime Minister Recep Tayyip Erdogan that Britain must apologise.

"In recent years British forces have violated international law and crossed the Iranian border. Britain should apologise to Iran," he said.

Iran has however said it will examine "in a positive way" to a Turkish request to free Turney and for the Turkish ambassador to see the Britons.

Britain said it was giving "serious consideration" to a diplomatic note from Iran, which protests at the sailors' "illegal act" but does not call for an apology.

Tehran initially said the woman would be released "within a day or two," but backed off on Thursday, citing Britain's "incorrect" attitude after London announced the suspension of ties and took the dispute to the United Nations.

After more than four hours of haggling and strong Russian reservations, the Security Council voiced "grave concern" and urged Tehran to allow "consular access" to the Britons who are being held in a secret location.

The council called for "an early resolution of the problem, including the release" of the 15.

But Britain had wanted to call for the sailors' "immediate release" and to note they were in Iraqi waters when detained.

Iran's UN mission responded by accusing the Council of being "exploited," while leading hardline cleric warned Britain to stop its "bullying" tactics and also warned European nations not to interfere.

However, at a meeting in Germany, EU foreign ministers were set to show their solidarity with Britain.

Both Britain and Iran have produced maps and global positioning system (GPS) coordinates to back their cases over where the sailors were when they were seized.

Britain has called the detentions an "ambush" and said Iran had changed the GPS coordinates of the two British patrol boats to make it appear they were in Iranian waters.

The United States, which has been conducting naval exercises in the Gulf involving two nuclear-powered aircraft carriers, has also given strong backing to its British ally.

Iran meanwhile released the text of a second letter written by Turney in which she was quoted as saying that British troops should leave Iraq.

"Isn't it time to start withdrawing our forces from Iraq and let them determine their own future?" Turney was quoted as saying in the letter to her member of parliament.

London was quick to condemn the letter, with Beckett calling it "outrageous and cruel".