Washington (AFP) - The US Treasury Department on Thursday announced sanctions against three of Venezuelan President Nicolas Maduro's stepsons, a Colombian businessman and six others for running a "corruption network" that profited from emergency food imports.

The US has in recent months escalated sanctions against Venezuela, which is struggling with a political and economic crisis that the United Nations says has left a quarter of its 30 million people in need of humanitarian aid.

The new restrictions target Maduro's stepsons Walter Jacob Gavidia Flores, Yosser Daniel Gavidia and Yoswal Alexander Gavidia Flores, whom the US says collaborated with Colombian businessman Alex Nain Saab Moran to profit off importing emergency food into the country as it struggled with rising malnutrition.

"What Treasury has described today is an extraordinarily elaborate network, whose purpose is to steal food from the poorest Venezuelans and build up profits for regime members and their families," a senior US official said on condition of anonymity.

As its economic crisis worsened, Venezuela's government in 2016 created a program to provide subsidized food to the poor, which Saab and a business partner organized so that food would be imported "at the most profitable rate for themselves," Treasury said in a statement.

"Under Maduro's watch, Saab reaped substantial profits and imported only a fraction of the food needed for the CLAP program," Treasury said.

It added that he "laundered hundreds of millions of dollars in corruption proceeds around the world," while paying off Maduro's stepsons for access to contracts.

The Treasury sanctions block Saab, Maduro's stepsons as well as six others involved in the alleged scheme from accessing the US financial system or doing business there.

Also sanctioned are 13 companies registered around the world that Treasury said were part of "a sophisticated network of shell companies" involved in the food importation scheme.

In January, National Assembly Speaker Juan Guaido declared himself acting president, branding Maduro an "usurper" over his re-election last year in a poll widely believed to have been rigged.

But despite the support of some 50 countries including the US, Guaido has been unable to dislodge him from power.

Representatives of the two sides have in recent weeks been negotiating in Barbados to resolve the political impasse.