Two Arab sailing boats carrying illegal drugs possibly linked to al-Qaeda have been seized in the northern Arabian Sea, the United States Navy says.
On Friday, the US Navy seized a large haul of hashish in the Gulf
The drugs on the wooden dhows included heroin with a street value of at least $3m, it said in a statement.
Twenty-one crew members were detained during an operation by the cruiser USS Philippine Sea on Saturday.
It is the second drugs haul in the region in recent days, as the US steps up efforts to tackle al-Qaeda funding.
On Friday, the navy said the USS Decatur had seized almost two tons of hashish valued at up to $10m aboard a boat near the Straits of Hormuz.
Of the 12 people detained in that operation, the US believes three have links to al-Qaeda.
"We are investigating potential al-Qaeda connections to these operations," Rear Admiral Jim Stavridis from the US Navy said on Saturday.
Smuggling routes in the region are known to be used by al-Qaeda, says the US military - which describes the seizures as "a vital part of winning the global war on terror".
The two boats were first spotted on Thursday and for 48 hours were tracked across the region, the navy says.
After boarding the first ship, it uncovered 67 kilogrammes (150 pounds) of methamphetamines.
The US Navy statement said the second ship attempted to flee, and its crew tried to dump their cargo.
About 200 white bags were thrown overboard during the chase which was filmed by a US Navy aircraft.
When the boat was finally intercepted, two remaining bags containing 38kg (85 pounds) of substance believed to be pure heroin were found.