TEHRAN, Iran — Tehran warned today that it will take strong action against five detained British sailors if it is proven they had "bad intentions" when their racing yacht entered Iran's Persian Gulf waters and was seized.

The detention could heighten tensions between Iran and major world powers, including Britain, that are demanding a halt to Tehran's controversial nuclear program.

London rushed to keep the incident from getting tangled up in the two nations' disputes — wary of how political tensions have snarled attempts to free three Americans arrested by Iran this summer after they strayed across the border from Iraq, reportedly by accident during a hike.

British Foreign Secretary David Miliband said "there is certainly no question of any malicious intent on the part of these five young people."

Britain says the yacht, called Kingdom of Bahrain, drifted inadvertently into Iranian waters while en route from Bahrain to a race off Dubai when Iranian forces stopped it Wednesday.

"This is a human story ... It's got nothing to do with politics, it's got nothing to do with the nuclear enrichment program," Miliband said.

"We are keen this be resolved as soon as possible," he said, telling reporters that London has been in touch with Iranian authorities since the seizure.

The seizure could also flare up the longtime rivalry between Iran and Bahrain, since the 60-meter (yard) yacht was the pride of a high-profile racing program sponsored by the tiny island nation's king, Sheik Hamad bin Isa al-Khalifa. Bahrain contacted Iranian authorities, telling them the entry into Iranian waters was unintentional and asking for the crew's release, Foreign Ministry official Youssef Ahmed said, according to the state news agency.

But the head of Iranian President Mahmoud Ahmadinejad's office said Iran will prosecute the Britons if they intended to "violate the national security" of Iran.

"Naturally if bad intentions on the part of these individuals are proven, there will be a serious and strong attitude toward them," Esfandiar Rahim Mashai said, according to the Fars news agency. "The decision will be up to the judiciary, which is independent from the administration."

The five were detained by Iran's elite Revolutionary Guard, Fars reported. The Guard, which runs its own naval forces, has the responsibility of protecting Iran's Persian Gulf waters. The Guard's navy chief, Gen. Ali Reza Tangsiri, said that if the five were stopped in the Gulf it would be by the Guard — though he did not confirm the detention.