Speaking in a television interview on GMTV on Tuesday, Blair described the group's capture as "unjustified and wrong."

"I hope we manage to get them to realize they have to release them," the British leader said. "If not, then this will move into a different phase."

When asked to explain what he meant, Blair said Iran needed to understand that "we cannot have a situation where our servicemen and women are seized when actually they are in Iraqi waters under a UN mandate, patrolling perfectly rightly and in accordance with that mandate, and then effectively captured and taken to Iran."

Germany exerting pressure

The German foreign ministry said on Tuesday it had called in the Iranian ambassador to Berlin and reiterated a demand for the immediate release of the 15 British detainees.

A ministry spokeswoman said ambassador Mohammad Akhondzadeh was told that Iran was obliged to give Britain consular access to the sailors. He was also told that the Islamic republic will be held responsible for their safety, she said.

Germany holds the rotating presidency of the European Union. The 27-member bloc has vowed to do everything possible to secure the release of the 14 British men and one woman who were seized by its forces in the Gulf last Friday.

Iran claims they had entered its waters illegally and has defied mounting pressure to free the group, saying Monday that they were being interrogated.

Iran refusing to budge

The Iranian government said on Tuesday it rejected any efforts by the UK to "politicize" the case.

"They have been arrested for an illegal act and therefore relevant legal procedures must be effected," Deputy Foreign Minister Mehdi Mostafavi was quoted by ISNA news agency as saying.

"They have violated Iranian waters and we just have to clarify through legal channels whether this British violation was deliberately or accidentally," Mostafavi said.

Iran condemned Blair's comments Tuesday as "provocative."

"The media campaigns and provocative ... remarks regarding the
violation of Iranian territorial waters by the British sailors are doing nothing to help settle the affair," said foreign ministry spokesman Mohammad Ali Hosseini. "The British service personnel entered Iranian waters illegally and the case will follow its legal and judicial course."

The Iranian government on Tuesday repeated statements that the group were safe but refused to confirm reports they had been taken to Tehran.

The British broadcaster BBC said it had been told that the sailors were being held at an Iranian Revolutionary Guards Corps base in the Iranian capital.

"They are in completely good health. Rest assured that they have been treated with humanitarian and moral behavior," Mohammad Ali Hosseini, a spokesman for the Foreign Ministry, told the Associated Press news agency.

Territorial dispute

Britain has categorically rejected Iranian allegations that the group, all crew members of the frigate HMS Cornwall, had violated Iranian waters. It said the eight sailors and seven marines were carrying out a routine search of a vessel suspected of smuggling in what Britain insists were Iraqi waters.

The group were taken at gunpoint by in the mouth of the Shatt al-Arab waterway, which divides Iran and Iraq.

Early this month, Iran released a German tourist who was imprisoned for more than 16 months after his boat accidentally strayed into restricted waters during a fishing excursion in the Persian Gulf.

Donald Klein said during a press conference on his return to Germany that the Iranian government "needed to learn it couldn't just capture people in order to exert political pressure."

However, Klein also said he had not been mistreated during his imprisonment.