National Assembly leader Juan Guaido also took to Twitter to demand the government free Weddle, "who was kidnapped by a regime that usurps functions and tries, without success, to hide the truth of what is happening in our country".
Waiting for Mr Guaido at the country's main airport, Mr Kriener spoke to media and said he hoped the leader of the National Assembly would have a safe return.
Guaido declared himself "interim president" in January.
More than 50 countries, including Germany, have recognized Guaido as the legitimate leader of Venezuela. Germany followed suit in early February.
The arrest risks further escalating tensions between the government of Nicolas Maduro and the USA, which along with more than 50 other countries has recognised National Assembly leader Juan Guaidó as Venezuela's legitimate president.
Addressing crowds of supporters after touching down in Caracas, he said: "We are going to achieve the end of the usurpation very soon in Venezuela".
European countries should "adopt a constructive balanced attitude" toward Venezuela's political crisis, instead of "encouraging the path of coups and violence (and) facilitate a peaceful and negotiated solution between the Venezuelan camps", it added.
Venezuelan opposition leader Juan Guaido, who has been recognized as interim president by the US and more than 50 other countries, arrived for a session of the opposition-led National Assembly, as a bitter political standoff with President Nicolas Maduro continues. Their mother, Sherry Weddle, said that the U.S. Embassy contacted the Ministry of Foreign Affairs, but have yet to hear back.
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Venezuela's Information Ministry did not immediately respond to a request for comment on his release.
Venezuelan leader Nicolas Maduro has cut ties with Colombia after opposition leaders used the neighboring Andean nation as a launching point for humanitarian aid meant to undermine his authority.
WPLG, one of the outlets for which Weddle worked, added that he was at the main Caracas-area airport waiting for a US -bound flight.
Camacho was released in the evening after 12 hours in custody, the union said, while Miami television station WPLG Local 10 said Weddle had also been released and was at the main Caracas-area airport waiting to board a USA -bound flight.
"Maduro had two options today", Weddle said.
"The United States is putting foreign financial institutions on notice that they will face sanctions for being involved in facilitating illegitimate transactions that benefit Nicolas Maduro and his corrupt network", Bolton said in a statement.
The U.S. revoked 49 visas last week and has imposed multiple rounds of sanctions as part of a campaign to force Maduro to turn over power to Guaido.