The U.S. said that it is pulling its last remaining diplomats from Venezuela, saying their continued presence at the country's embassy in Caracas had become a “constraint” on U.S. policy as the Trump administration aggressively looks to oust socialist President Nicolas Maduro.

The announcement came from Secretary of State Mike Pompeo in a tweet shortly before midnight Monday and comes as Venezuela struggles to restore electricity following four days of blackouts around the country.

The U.S. has led an international effort to replace Maduro with opposition leader Juan Guaido, who vows to hold a new presidential election. Guaido is backed by some 50 countries, while Maduro maintains support from countries such as China, Russia and Cuba.

Maduro ordered all U.S. diplomats to leave Venezuela in late January because of its support for Guaido, but he later retreated and allowed them to stay. The U.S. still withdrew the bulk of embassy personnel, leaving a skeletal staff led by career foreign service officer James Story.

Pompeo said the remaining diplomats would be out of Venezuela by the end of the week but gave no indication of future policy steps despite past warnings that “all options,” including the use of military force, are on the table for removing Maduro.

The move came after another day of chaos as power outages that began last Thursday evening continued to cause problems for Venezuelans, leaving them with little power, water and communications.

People converged on a polluted river to fill water bottles in Caracas, and scattered protests erupted in several cities.

A 3-year-old girl with a brain tumor languished in a Caracas hospital, awaiting treatment after doctors started surgery but then suspended the operation when nationwide power outages first hit on Thursday, said the girl's fearful mother, who only gave her first name, Yalimar.

“The doctors told me that there are no miracles,” said Yalimar, who hopes her daughter can be transferred Tuesday to one of the few hospitals in Venezuela that would be able to finish the complex procedure.

The girl's story highlighted an unfolding horror in Venezuela, where years of hardship got abruptly worse after the power grid collapsed. On Monday, schools and businesses were closed, long lines of cars waited at the few gasoline stations with electricity and hospitals cared for many patients without power. Generators have alleviated conditions for some of the critically ill.

President Nicolas Maduro said on national television Monday night that progress had been made in restoring power in Venezuela. He also said two people who were allegedly trying to sabotage power facilities were captured and were providing information to authorities, though he gave no details.

Guaido, who heads the opposition-controlled congress, and the United States say Maduro's claims that the U.S. sabotaged the power grid with a “cyberattack” are an attempt to divert attention from the government's own failings.

There have been acts of kindness during Venezuela's crisis: People whose food would rot in refrigerators without power donated it to a restaurant, which cooked it for distribution to charities and hospitals.

The blackouts also have hit the oil industry. The country hasn't shipped $358 million in oil since the power failures started, and “the whole system is grinding to a halt,” said Russ Dallen, a Miami-based partner at the brokerage firm Caracas Capital Markets.

Two large tankers are sitting empty at the Jose offshore oil-loading dock, and at least 19 other ships are waiting their turns there, Dallen said.

Engineers have restored power in some parts of Venezuela, but it often goes out again. There have been a few protests in Caracas and reports of similar anti-government anger elsewhere. Guaido tweeted about reports of looting in some cities, but details were difficult to confirm.

Security forces in the city of Maracaibo dispersed “criminals” trying to take advantage of the power cuts, Mayor Willy Casanova told local media. However, numerous videos posted on social media that purported to be from Maracaibo showed crowds roaming the streets and people running from looted, damaged buildings with no police in sight.

In Caracas, some people reported more sightings of “colectivos,” a term for armed groups allegedly operating on behalf of the state to intimidate opponents.

The mood in Caracas was desperate.

Marian Morales, a nurse working for a Catholic youth group, and several colleagues handed out diapers and food from a car parked near a hospital. Police and men in civilian clothing ordered them to leave, saying they didn't have permission.

Morales said the needy are cautious about approaching to collect the handouts because of the presence of security forces.

Early Monday, an explosion rocked a power station in the Baruta area of Caracas. Residents gathered to look at the charred, smoldering equipment.

Guaido said three of four electricity transformers servicing the area were knocked out. He has blamed the blackouts on government corruption and mismanagement.

Winston Cabas, the head of Venezuela's electrical engineers union, which opposes the government, disputed government allegations that the country's main hydroelectric dam was sabotaged last week. He blamed a lack of maintenance as well as the departure of skilled workers from the troubled country over the years.

“The system is vulnerable, fragile and unstable,” he said.

Spain's airline pilots union asked for Spanish airline Air Europa to stop flying to Venezuela after one of its crews was attacked at gunpoint in Caracas. The Sepla union said two pilots and eight more crew members of a flight from Madrid were assaulted on Saturday while going from the airport to their hotel in the Venezuelan capital. None of the crew members was injured.

Air Europa responded by ordering the crews of flights to Venezuela to not spend the night in the country, according to the union.

The administration of U.S. President Donald Trump imposed sanctions on a Moscow-based bank jointly owned by Russian and Venezuelan state-owned companies, alleging it tried to circumvent U.S. sanctions on the South American country. The U.S. said it is targeting Evrofinance Mosnarbank for supporting Petroleos de Venezuela SA, the state oil company previously targeted by sanctions in January.

Evrofinance said it was carrying out its activities normally despite the announcement and pledged to “meet its obligations to the clients and partners in full.”

The U.S. and the other governments that recognize Guaido as Venezuela's interim president say Maduro wasn't legitimately re-elected last year because opposition candidates weren't permitted to run. Maduro says he is the target of a U.S. coup plot.

Fabiola Sanchez and Scott Smith report for the Associated Press. Associated Press writer Christopher Torchia contributed to this report.