The U.S. State Department raised its travel advisory for Venezuela to level 4 and warned that Americans have been arbitrarily detained "for long periods" in the politically unstable nation.

"Do not travel to Venezuela due to crime, civil unrest, poor health infrastructure, and arbitrary arrest and detention of U.S. citizens," said the advisory, issued Tuesday.

It warned that violent crime is common and that areas across the country are seeing shortages of basic necessities like food and water. It also noted the volatility of protests.

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"Demonstrations typically elicit a strong police and security force response that includes the use of tear gas, pepper spray, water cannons, and rubber bullets against participants and occasionally devolve into looting and vandalism," the advisory said.

The announcement was made five days after the State Department ordered non-emergency government workers and their families to leave the country as two men remain locked in a struggle for power. Last week, President Trump recognized opposition leader Juan Guaidó as the country's legitimate interim president, prompting Nicolas Maduro to cut diplomatic ties with the U.S.

On Thursday, U.S. Secretary of State Mike Pompeo reaffirmed the U.S. backs Guaidó, who declared himself president.

"The time for debate is done. The regime of former President Nicolas Maduro is illegitimate," Pompeo said.

Venezuela has suffered from economic turmoil and a humanitarian crisis under Maduro. The conditions have prompted more than 2 million people to flee, according to the United Nations.