The foreigners were intercepted in the locally hired boat on Monday off the Maldives' southernmost atoll of Addu heading to Diego Garcia several hundred kilometres away, said Mohamed Shareef, a minister attached to the president's office.
He did not give the nationalities of the seven, but local newspaper Haveeru said they were Germans and Italians.
Diego Garcia, a British territory in the Indian Ocean, is currently leased to the United States, which operates a highly-guarded military base used for bombing raids on Afghanistan and Iraq.
The Maldives is holding the group for leaving the honeymoon islands illegally.
"We are continuing investigations and so far the foreigners have told us that they were on a whale-watching expedition. But you don't step out in rough weather when there are eight-foot waves to look for whales," Shareef told AFP.
Shareef said the group, whose governments have been contacted since the arrests, had chartered the boat at a rate of $8,000 a day.
"They had been looking for a (trawler) captain to take them to Diego Garcia and were willing to pay a very high price," he said by phone from the Maldives capital island Male.
Shareef said it was extremely unlikely the trawler would have reached the main island of Diego Garcia, some 700 kilometres (435 miles) from Addu, given the tight security there.
"Maldivian fishermen know very well that if they stray into that territory their vessels are confiscated," he said.
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