LONDON: Somali pirates have demanded a $7 million ransom for a British couple captured on their yacht in the Indian Ocean, according to a phone call from a man purporting to be a member of the gang broadcast by the BBC on Friday.

Gunmen kidnapped Paul and Rachel Chandler, both in their 50s, last Friday while they sailed in international waters north of the Seychelles and took them to the Somali coast.

"We only need a little amount of $7 million," the BBC quoted the unnamed caller as saying. "If they do not harm us, we will not harm them."

Pirates have plagued busy shipping lanes off the coast of Somalia for several years. Foreign warships from 16 nations are patrolling the area to try and prevent hijacks, but the sea gangs are now hunting for ships far into the Indian Ocean.

A Foreign Office spokesman in London said the British government was aware of the reported ransom demand but could not confirm its authenticity.

In a tearful phone call to her brother Stephen Collett, Rachel Chandler said that they were coping with the pressure and their captors had given them food and water.

A pirate called Hassan told Reuters by telephone from the coastal town of Haradheere earlier this week that the gang was holding the couple on a hijacked Singaporean container ship.

"After we understood the British navy might attack us, we took the hostages off the yacht into the Singaporean ship to bring them safely here," he said.

The couple's niece Leah Mickleborough told the BBC that the family was aware of the ransom demand report and that they would "look into it".

The pirate gangs -- some made up of former fisherman angered by the presence of foreign fishing fleets in Somali waters -- and their backers within Somalia and abroad have made tens of millions of dollars in ransoms.