Venezuela on Wednesday declared the German ambassador in Caracas "persona non grata" for meddling in its internal affairs and ordered he leave the country in 48 hours.

The expulsion of Daniel Martin Kriener "is due to his repeated acts of interference in the country's internal affairs," the Venezuelan Foreign Ministry said in a statement.

Kriener was reportedly among a handful of foreign diplomats who went to the airport on Monday to greet Juan Guaido on his return from a tour of Latin American countries that support Venezuela's right-wing opposition movement.

Guaido, president of the National Assembly, declared himself "interim president" on Jan 23. The United States immediately recognized Guaido's temporary presidency, followed by Germany and some other countries in early February.

The 35-year-old had defied a ban on leaving the country to embark on a 10-day tour of South American allies. He remains free despite the threat of arrest by the government.

The Venezuelan government believed that Washington's approval of Guaido as the country's interim leader aimed to oust the government of President Nicolas Maduro, and open up its vast oil reserves as well as gold deposits to US corporations.

Maduro on Wednesday called on his supporters to hold "anti-imperialist" marches on Saturday.

"Venezuela is irrevocably free and independent, which is why actions by diplomatic representatives that implicate meddling in matters that are the exclusive realm of the Venezuelan people and state authorities are not and will not be allowed," the Foreign Ministry said.

It added that 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".

After the expulsion order, German Foreign Minister Heiko Maas said he had decided to recall Kriener to Berlin for consultations. "This is an incomprehensible decision that aggravates the situation and does not contribute to de-escalation. Our, Europe's, support for Juan Guaido is unbroken. Ambassador Kriener is doing excellent work in Caracas, including in recent days."

Meanwhile, Washington is pursuing new diplomatic and economic initiatives to support Guaido's bid for a transitional government in Venezuela, US National Security Adviser John Bolton said on Wednesday.

The US government has imposed oil sanctions in Venezuela as well as sanctions on high-ranking members of the Venezuelan security forces and other senior officials. The US visas of other Venezuelan officials and their relatives have been revoked.

Michelle Bachelet, the United Nations' high commissioner for human rights, said on Wednesday that US sanctions have worsened Venezuela's crippling economic and political crisis.

Xinhua, AP and Reuters contributed to this story.