MIAMI (AFP) - US authorities intercepted a suspicious airplane leaving Florida over the weekend, discovering weapons and thousands of dollars in cash on board.

Agents from the Fort Lauderdale Marine Unit, north of Miami, were alerted Saturday (Aug 15) to the movement of a Learjet aircraft connected to an ongoing investigation, according to a statement from Customs and Border Protections released Tuesday.

Officials from multiple federal agencies responded to stop the plane, which was headed for the Caribbean island of St Vincent.

They arrested two Venezuelans, whose identities have not been revealed, and seized 18 assault rifles, six shotguns, 58 semi-automatic pistols, $20,312 (S$27,730) in cash and $2,618.53 in endorsed checks, the statement said.

The operation was a CBP mission conducted along with Homeland Security Investigations and the Federal Aviation Administration, among other agencies.

According to Venezuelan opposition deputy Carlos Paparoni, the airplane is linked to Colombian businessman Alex Saab, accused of corruption relating to a food program run by President Nicolas Maduro.

Saab is currently imprisoned in Cape Verde.

The aircraft "belongs to a company owned by Roswell Rosales, a pilot of Alvaro Pulido Vargas, a partner of Maduro's front man Alex Saab," Paparoni wrote on Twitter.

He added in a second tweet that one of Rosales's frequent passengers is Carlos Rolando Lizcano, "a key part of Alex Saab's criminal organisations."

"The world is getting smaller for them, their criminal organisation is naked," Paparoni wrote.

Saab was accused in Miami of money laundering, and was arrested in June during a technical stopover of his plane in Cape Verde.

On August 5 a Cape Verde court 5 gave the green light to extradite Saab to the United States.