The car bomb was driven into two police vehicles that had stopped at the intersection and several policemen standing nearby on Monday, said police Captain Talib Thamir.
He said nine policemen and an Iraqi civilian walking nearby were killed and two policemen wounded.
Meanwhile, a US military press release on Monday said eight US servicemen were killed and another wounded in a series of attacks over the weekend throughout Iraq.
Three marines and a sailor were killed on Saturday night when a car driven by a car bomber exploded in Haditha, 260km northwest of Baghdad, the military said in a statement.
The US military also said on Monday that its forces had launched an offensive against anti-US fighters in western Iraq near the Syrian border, killing about 75 fighters in the first 24 hours.
It said the offensive, being conducted with US air support in al-Anbar province north of the Euphrates River, was targeting a sanctuary for foreign anti-US fighters and an alleged smuggling route.
Samarra has witnessed many
attacks on US and Iraqi forces
The brief US statement did not say when the offensive had begun, how many troops were involved nor whether there had been any American casualties.
The Chicago Tribune reported on Monday that more than 1000 US troops supported by fighter jets and helicopters had attacked villages in and around Ubaidi, a city not far from the Syrian border on Sunday.
The report, by a journalist "embedded" with US forces, said the offensive "was seeking to uproot a persistent insurgency in an area that American intelligence indicated has become a haven for foreign fighters flowing in from Syria".
It said the offensive was expected to last several days.
Elsewhere, one soldier was killed and another wounded on Sunday by an explosion during a patrol near Samarra, north of the capital.
Another soldier was killed by small arms fire near Samarra on Sunday.
And two more service personnel, assigned to a marine division, were killed on Sunday in an explosion near Khalidiyah, close to the city of Ramadi, west of the capital.
The US toll brings to 1603 the number of military personnel killed in Iraq since March 2003, according to the independent Iraq Coalition Casualty Count website, quoting Pentagon figures.
"They are believed to be from Sadr City," a Shia district of northern Baghdad, according to the officer, who suggested they were killed two days ago.
Also on Monday, the bodies of eight Iraqi civilians, tortured, then executed with a bullet to the back of the neck, were found on the southern outskirts of Baghdad, the Iraqi army and medics said.
"The bodies were found at 6am in wasteland north of Yusufia 40km south of Baghdad and taken to Mahmudiyah hospital," army Captain Ahmad Husain said.
The victims had been tortured
and shot in the back of the head
Relatives of the victims - all believed to be from the same family - said they had been missing since Friday when they went to visit relatives in southern Baghdad.
On Friday, the bodies of 14 Sunni farmers from a community south of Baghdad were recovered on the outskirts of Sadr City. They too had been tortured and shot in the back of the head.
Sunni associations said the farmers were kidnapped by men disguised as policemen.
In other violence on Sunday, four Iraqis were killed in two roadside bombings and gunfire in Mosul, 360km northwest of Baghdad, the US military said.
One anti-US fighter was also killed and another wounded in a clash with a US-Iraqi patrol.
In southern Baghdad, armed men shot and killed Zuba Yass, a senior official in Iraq's Transport Ministry, and his driver, police and transport officials said.