BAGHDAD — Iraq’s Shiite-led government issued an arrest warrant Monday for the Sunni vice president, accusing him of running a hit squad that assassinated government and security officials — extraordinary charges a day after the last U.S. troops left the country.

The vice president, Tariq al-Hashemi, left Baghdad on Sunday for the semiautonomous Iraqi region of Kurdistan, presumably hoping that Kurdish authorities would not turn him in. Investigative judges banned him the same day from traveling outside of Iraq.

The move against the country’s highest-ranking Sunni official marked a sharp escalation in sectarian tensions, raising fears of a resurgence of large-scale bloodshed. Although many Iraqis welcomed the American withdrawal, ending the nine-year U.S. war, there are also considerable fears here that violence will worsen.

“Iraq is slipping into its worst nightmares now, and Iraqi people will pay a high price because of the struggle among political blocs after the pullout of U.S. troops,” said Baghdad-based political analyst Kadhum al-Muqdadi, a Shiite.

White House spokesman Jay Carney said the Obama administration had expressed its concerns to all of the parties involved regarding the issuing of the warrant.

“We are urging all sides to work to resolve differences peacefully and through dialogue in a manner consistent with the rule of law and the democratic political process,” Carney said.

Sunnis suspected the charges against al-Hashemi were politically motivated.

Al-Hashemi is an old rival of Prime Minister Nouri al-Maliki, and the arrest order came two days after the main Sunni-backed political bloc, Iraqiya, suspended its participation in parliament because al-Maliki refused to give up control over key posts.

Al-Maliki, a Shiite, has made a series of moves in recent months to consolidate his hold on power. Hundreds of former members of Saddam Hussein’s Baath Party have been rounded up, allegedly as security threats, although no proof has been given. In Tikrit, Saddam’s hometown, arrests have become so commonplace that whenever a police car shows up, young men flee from the street.

State-run television aired what it characterized as confessions by men said to be working as bodyguards for al-Hashemi. The men said they killed officials working in Health and Foreign Ministries as well as Baghdad police officers, and that they received $3,000 from al-Hashemi for each attack.

“An arrest warrant has been issued against Vice President al-Hashemi under the terrorism law and five judges have signed this warrant,” said Interior Ministry spokesman Adil Daham said as he waved a copy of the order.

Al-Hashemi, one of two vice presidents in Iraq, could not be reached for comment.