"We're tracking a US Navy sailor was detained in Venezuela by law enforcement in that country," the official said on condition of anonymity, without providing further details on the detention, which reportedly occurred late last month.

The South American country was rocked by protests when President Nicolas Maduro was declared the winner of a disputed July 28 election, with dozens killed and more than 2,400 people arrested.

The opposition claims it won by a landslide, and the United States, the European Union and several Latin American countries have refused to recognize Maduro as having won without seeing detailed voting results.

Washington on Monday seized Maduro's plane in the Dominican Republic and flew it to Florida, a move the Venezuelan leader condemned as "piracy" but which Washington said was necessary due to sanctions violations.

The following day, Washington denounced an arrest warrant issued in Venezuela for opposition presidential candidate Edmundo Gonzalez Urrutia and warned of further action against Maduro.

The US State Department has warned Americans against traveling to Venezuela for reasons including crime, unrest and wrongful detention.

"There is a high risk of wrongful detention of US nationals in Venezuela. Security forces have detained US citizens for up to five years," the department's Venezuela travel advisory says.

"The US government is not generally notified of the detention of US citizens in Venezuela or granted access to US citizen prisoners there," it says.