U.S. President Barack Obama on Monday ordered the sanctions recently approved against top Venezuelan officials to be implemented and declared a "national emergency" over the "extraordinary risk" that, he said, the Venezuelan situation poses for U.S. security.

In an executive order, Obama "implements and expands" the sanctions on certain Venezuelan citizens included in a law approved last December, as White House spokesman Josh Earnest explained in a communique.

"I hereby report that I have issued an Executive Order ... declaring a national emergency with respect to the unusual and extraordinary threat to the national security and foreign policy of the United States posed by the situation in Venezuela," wrote Obama in a letter sent to House Speaker John Boehner.

"The order does not target the people of Venezuela, but rather is aimed at persons involved in or responsible for the erosion of human rights guarantees, persecution of political opponents, curtailment of press freedoms, use of violence and human rights violations and abuses in response to antigovernment protests, and arbitrary arrest and detention of antigovernment protestors, as well as the exacerbating presence of significant public corruption in that country," the letter reads.

The declaration of a "national emergency" is a tool whereby the U.S. president may apply sanctions against a country under certain circumstances and which allows him to take measures going beyond what Congress has approved.

With the executive order, Obama announces the imposition of sanctions on seven top Venezuelan officials, whose assets in the United States will be frozen and who are forbidden from entering this country.

Among the sanctioned officials are Gustavo Enrique Gonzalez Lopez, the general director of the SEBIN national intelligence service, and the former director of operations for the Bolivarian National Guard, or GNB, Antonio Jose Benavides Torres.

The list also includes Justo Jose Noguera Pietri, the former commanding general of the GNB; National Public Prosecutor Katherine Harrington; National Police director Manuel Eduardo Perez Urdantes; former SEBIN chief Manuel Gregorio Bernal Martinez and Miguel Alcides Vivas Landino, the inspector general of the Venezuelan armed forces.

So far, the U.S. government has not made public the list of people sanctioned in the law approved by Congress in December, and so it is not known if these seven individuals are also on the other list.

The executive order signed on Monday also authorizes the Treasury to impose more sanctions on those who are determined to have promoted actions or plans "that undermine democratic processes or institutions" and those who violate human rights in Venezuela, according to the White House.