BAGHDAD, Iraq - U.S. National Intelligence Director John Negroponte met Friday with the Iraqi prime minister, in the second visit this week by a top U.S. official amid spiraling violence that included four American deaths and the discovery of 56 bodies bearing signs of torture.

The bodies found scattered around the Iraqi capital were of men between 20 and 45 years old, and all were apparent victims of sectarian death squads, police said Friday.

All wore civilian clothes and had been bound at the wrists and ankles, police Lt. Mohammed Khayon said. He said the bodies showed signs of having been tortured, a common practice among religious extremists who seize victims from private homes or from cars and buses traveling the capital's dangerous streets.

Such murders almost always go unsolved and Khayon said the police had no solid information on the victims' identities or their killers.

Shiite militiamen have been blamed for many of Baghdad's sectarian slayings, which exploded in number following the February bombing of an important Shiite shrine in the Iraqi city of Samarra.

Violence against Iraqis has grown unabated in the past month, with more than 1,300 killed since Oct. 1.

Apparently fearing still more bloodshed after Sunday's expected announcement of a verdict in the trial of former Iraqi leader Saddam Hussein, Iraq's defense minister has canceled leave for all army officers.

Defense Minister Abdul-Qader al-Obeidi was heard issuing the order in video of a meeting between Prime Minister Nouri al-Maliki and senior military and security officials, in which al-Maliki upbraided them for failing to stop the capital's unbridled violence.

"All vacations will be canceled and all those who are on vacation must return," al-Obeidi said, adding that reserve soldiers would be called up within 12 hours.

The U.S. military announced the deaths of three soldiers in Baghdad and a Marine in the western province of Anbar.

A brief statement said the three soldiers died Thursday when the vehicle they were riding in was struck by a roadside bomb in eastern Baghdad. A separate announcement said one Marine died from injuries "due to enemy action" Thursday in Anbar.

October was the fourth-deadliest month for U.S. forces since the war began, with the deaths of 105 service members reported.

The unannounced Negroponte visit comes five days after the arrival of National Security Adviser Stephen Hadley, who flew to Baghdad after the Iraqi leadership issued a series of bitter complaints about U.S. tactics in the country.

Al-Maliki met with Negroponte in the Iraqi leader's office in Baghdad's heavily fortified Green Zone, according to the prime minister's spokesman.

The spokesman, Yassin Majid, said the visit was part "of a continuing series of meetings between the Iraqi government and the U.S. administration." He did not elaborate. U.S. Embassy officials confirmed Negroponte was in the capital but would not comment further.

Video from the prime minister's office showed Negroponte and U.S. Ambassador Zalmay Khalilzad greeting al-Maliki, with three kisses on the check.

Negroponte's comments were difficult to hear on the tape, but he was believed to have said President Bush was not tired by the heavy election campaigning for the coming U.S. midterm election in response to an inaudible question from al-Maliki.

Relations between the United States and the Iraqi government have been strained in recent days after al-Maliki issued a series of bitter complaints, at one point saying he was not "America's man in Iraq."

Negroponte served as the American ambassador to Iraq before Khalilzad.

The Iraqi security chief, Mouwafak al-Rubaie, told the AP that Hadley had discussed the work of a five-man committee that al-Maliki and President Bush agreed to establish last week to deal with security issues and speeding the transition to Iraqi control over the country.

Hadley, whose visit also was unannounced, also presented some proposals concerning the training and equipping of Iraqi security forces as well as security plans.

U.S. voter support for the war is at a low point as the Nov. 7 midterm elections approach, and a top aide to al-Maliki has said he was using the Republicans' vulnerability on Iraq to leverage concessions from the Bush administration — particularly the speedy withdrawal of American forces from cities to U.S. bases in the country.

U.S. troops acting on intelligence reports raided a building in Mahmoudiya, about 20 miles south of Baghdad, killing 13 suspected insurgents, the military said.

The building was surrounded and stormed after those inside did not respond to demands to surrender, the military said in a statement e-mailed to media. Five people were killed inside the building, including one man wearing a vest rigged with explosives, while eight other men who fled were gunned down by troops on the ground and planes or helicopters circling above, the report said.

Several of those killed appeared to have been foreign fighters from outside Iraq, the report said. The report did not say if there were American casualties.

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