BAGHDAD, Iraq - At least 39 people were killed by insurgents and shadowy sectarian gangs, police reported Monday ¡ª continuing the wave of violence that has left nearly 1,000 Iraqis dead since the bombing last month of a Shiite Muslim shrine.

Two Iraqi women walk pass as Iraqi police tow away their damaged vehicle, which was targeted by a roadside bomb, in Baghdad, Iraq, Monday, March 20, 2006. Killers marked the third anniversary of the U.S.-led invasion of Iraq Monday with roadside bombings that killed at least seven policemen, and authorities reported finding 10 more bullet-riddled bodies dumped in the capital, one of them a 13-year-old girl. [AP]

As the Iraq war entered its fourth year, police found the bodies of at least 15 more people ¡ª including that of a 13-year-old girl ¡ª dumped in and near Baghdad. The discoveries marked the latest in a string of execution-style killings that have become an almost daily event as Sunni and Shiite extremists settle scores.

Sectarian killings have swept across Iraq since the Feb. 22 bombing of a Shiite Muslim shrine in Samarra. An Associated Press tally, including the deaths reported Monday, put the toll at 993 since the golden dome atop the Askariya shrine was left in rubble by two bombers, who are believed to remain at large.

Among those killed in scattered violence Monday were 10 policemen, who are prime targets for insurgents, most of them Sunni militants, trying to break the will of the mainly Shiite police force.

As night fell on Monday, a bomb struck a coffee shop in northern Baghdad, killing at least three civilians and injuring 23 others. The bomb was left in a plastic bag inside the shop in a market area of the Azamiyah neighborhood, police Maj. Falah al-Mohammadewi said.

At about the same time, gunmen killed two oil engineers leaving work at the Beiji refinery north of Baghdad. An electrical engineer and technician were gunned down at the nearby power station, Beiji police Lt. Khalaf Ayed Al-Janabi said.

Separately, the owner of a small grocery in downtown Baghdad was shot and killed.

In southeast Baghdad, also toward evening, a roadside bomb blew apart a minibus, killing four pilgrims returning from the holy city of Karbala, where millions of Shiite faithful gathered to mark the 40th and final day of the annual mourning period for Imam Hussein, grandson of the Prophet Muhammad. Five pilgrims on their way to Karbala were wounded in a drive-by shooting earlier in the day, police said.

Otherwise, the commemoration passed largely without incident and absent the violent bomb attacks that have hit pilgrims there over the past two years.

Authorities in Baghdad closed the international airport until Tuesday, citing the need to protect the Karbala commemoration, apparently from any attackers who might try to fly into the country.

And Jordanian authorities closed their border with Iraq until further notice to "prevent those without valid travel documents from entering the country," said Maj. Bashir al-Da'ajah, spokesman of Jordan's Public Security Department. The New York Times reported the border was closed because a large number of Palestinians living in Iraq were trying to cross into Jordan without proper documents.

Much of the violence targeted police officials:

*Roadside bombs ¡ª one just a few hundred yards from an Interior Ministry lockup in central Baghdad and one in a farming area near the so-called Triangle of Death south of Baghdad ¡ª killed at least seven police officials. A prisoner was also killed in the Interior Ministry bombing.

*A policeman in a joint American-Iraqi patrol was killed in Baghdad during fighting with insurgents, police said.

8A car bomb targeting a police checkpoint exploded in Baqouba, 35 miles northeast of Baghdad, killing one policeman, authorities said.

*In the northern city of Mosul, gunmen killed a policeman and an oil ministry official, police said.