President Nicolás Maduro announced on Monday the expulsion of the top US diplomat in Venezuela and two other embassy employees for allegedly conspiring with "the extreme right" to sabotage the economy and power grid.

The US embassy said it had not yet received notification and called the accusations unfounded.

Maduro made the announcement during a live TV appearance and said they had 48 hours to leave the country.

"Out of Venezuela," the leader shouted, then added in English: "Yankees go home!"

Maduro said a group of embassy officials that his government had been following for months was "dedicated to meeting with the Venezuelan extreme right, to financing it and feeding its actions to sabotage the electrical system and the Venezuela economy".

"I have proof here in my hands," he said, though he did not offer any details on the diplomats' alleged transgressions other than to say they met with opposition and labour leaders in the south-west state of Bolivar, which is home to a number of troubled state-owned foundries and Venezuela's main hydroelectric plant.

Expelled were charge d'affaires Kelly Keiderling, the top embassy official in the absence of an ambassador, consular officer David Moo and Elizabeth Hoffman, who works in the embassy's political section.

The latter two were identified by the embassy, which said it had not received official notification from the foreign ministry.

"We completely reject the Venezuelan government's allegations of US government involvement in any type of conspiracy to destabilise the Venezuela government," the US embassy said in a statement.

It said the recent trip by Keiderling, Moo and Hoffman consisted of "normal diplomatic engagement", adding: "We maintain regular contacts across the Venezuelan political spectrum, including the ruling party."

The expulsions come as Venezuela's economy looks increasingly troubled before municipal elections on 8 December. Annual inflation is at more than 45% and the government is running short of foreign currency.

Venezuela and the United States have been without ambassadors since 2010, when the late president Hugo Chávez refused to accept a newly named US ambassador. In 2008, Chávez expelled then-US ambassador Patrick Duddy in "solidarity" with Bolivia, which was booting the US ambassador there, but allowed him to return the following year.

Keiderling arrived at the embassy in July 2011 as deputy chief of mission after previously working in embassies including in Moldova, Kyrgyzstan, Botswana, the Dominican Republic and the US Interests section in Cuba.

The oil-rich Opec member country has been plagued by worsening power outages since 2010. The opposition blames neglect and poor maintenance, while alleging mismanagement and corruption at struggling state-owned aluminium, iron and bauxite foundries in Bolivar.

Maduro blames sabotage by the "extreme right" for the blackouts and food shortages, but has provided no evidence. Like Chávez, he has a history of making unsubstantiated accusations against the United States and his political opponents.

Last week, Maduro said he had cancelled a planned trip to New York to address the UN general assembly due to an unspecified US plot. Since his April election, Maduro has claimed five attempts to assassinate him have been foiled. In no instance did he provide evidence.

Opposition leader Henrique Capriles, in a tweet, called Monday's expulsions "pure smoke to mask that [Maduro] can't handle the country".

The last time Venezuela expelled US diplomats was on 5 March, when it ejected two military attaches for allegedly trying to destabilise the nation. That move came several hours before Maduro announced that Chávez had died of cancer.

Chávez governed Venezuela for 14 years, solidifying control of all branches of government as he won solid backing from the poor with generous social spending and blamed the United States for an unsuccessful attempt to overthrow him in 2002.

In recent years, however, Venezuela's woes have been compounded by corruption, rampant violent crime, worsening power outages and increasing shortages of food and medicines.

At the same time, Maduro's government has been accused by international human rights and press freedom groups of cracking down on free speech and independent media political activity.

An apparent thaw in US-Venezuelan relations appeared in the offing in early June after foreign minister Elias Jaua met with secretary of state John Kerry.

But Maduro scuttled it after Washington's ambassador to the UN, Samantha Power, accused Venezuela of a crackdown on civil society during her confirmation hearing the following month.

Maduro narrowly won elections in April over Capriles, who claims the victory was fraudulent.