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 Iraq.

The move against Iraq'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 U.S. withdrawal, ending the nine-year 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 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.

Sunnis suspected the charges against Hashemi were politically motivated. 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 Maliki refused to give up control over key posts.

Maliki, a Shiite, has moved 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.

State-run television aired what it characterized as confessions by men said to be working as bodyguards for Hashemi. The men said that they killed officials working in Health and Foreign Ministries as well as Baghdad police officers, and that they received $3,000 from 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," Interior Ministry spokesman Adil Daham said as he waved a copy of the order.

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

Since the 2003 U.S.-led invasion that toppled Hussein and his Sunni-dominated Baath Party regime, the Sunni minority has complained of attempts by the Shiite majority to sideline them.

Everyday relations between Sunnis and Shiites are much better than they were at the height of the insurgency, when neighbors turned on neighbors and whole sections of Baghdad were expunged of one Muslim sect or the other.

But an uneasy peace was achieved through intimidation and bloodshed. The number of Iraqi neighborhoods in which members of the two Muslim sects live side by side and intermarry has dwindled.

The forced segregation, fueled by extremists from both communities, has changed the character of the country. And it raises questions about whether the Iraqis can heal the wounds of the sectarian massacres now that the U.S. soldiers have left.

Toward the end of the U.S. occupation, many Sunnis came to feel that the U.S. military was treating them fairly, or at least more fairly than the Shiite-led government. They fear that the U.S. departure now means the loss of a protector.