A senior Iranian official said on Thursday that his country had "achieved its objectives" on the 13- day-old British sailors detention issue, the state television reported.

"Iran showed its will to defend its territorial integrity, we have achieved the objectives in pardoning the British sailors," former Foreign Minister Ali Akbar Velayati, who is now the foreign policy advisor to supreme leader Ali Khamenei, was quoted as saying.

The senior official also disclosed that Britain had sent an apology letter to Iran just one day before President Mahmoud Ahmadinejad announced the release of the sailors.

"Iran has a condition that Britain accepts the violation of Iranian waters and apologize, one day before their release, the ( British) prime minister (Tony Blair) sent a letter of apology," he said.

President Ahmadinejad on Wednesday made a surprise announcement during his press conference to release the 15 British sailors who were detained by Iran on March 23 due to their "illegal entry" of Iranian waters.

The Britons released by Iran had arrived at London's Heathrow airport on Thursday. Upon arrival, they were immediately transfer to naval helicopters and fly straight to Royal Marines Base Chivenor in southwest England, reports said.

Source: Xinhua