The eight British navy servicemen seized by Iran in a river between Iran and Iraq have been released after three days of detention in the country, British Foreign Secretary Jack Straw said Thursday.

They are now in the custody of British diplomats, Straw said in a short statement outside 10 Downing Street.

"I'm obviously very pleased indeed. I'm told that they are in very good spirits and were well cared for," Straw said.

According to the Foreign Office, the six Royal Marines and two sailors have boarded a plane with British diplomats on their way to the Iranian capital of Tehran.

The eight navy personnel and their three vessels were detained by the Iranian authority on Monday in the Shatt al-Arab waterway that runs along the border between Iraq.

British officials have said that the men may have mistakenly strayed over the maritime border between the two countries.

The British Ministry of Defense said in a statement that the personnel were from the Royal Navy training team based in southern Iraq and were delivering a boat from Umm Qasr to Basra, Iraq, when they were captured.

Their release follows three days of talks between British diplomats and Iranian officials.

Iran had initially said it would prosecute the men for "illegally entering Iranian territory."

After being detained by Iran, the men appeared on Iranian TV wearing blindfolds earlier in the week and apparently admitted entering Iranian waters illegally.

The arrests came at a time of strained relations between Britain and Iran.

Some Iranian people have staged a series of angry demonstrations outside the British Embassy in Tehran in recent weeks to protest at the occupation of Iraq.

Britain has also been strongly criticized for its role in helping draft a tough resolution on Iran at the International Atomic Energy Agency in Vienna last week.