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.

Other violence in Iraq Monday targeted more policemen.

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 and one prisoner.

A policeman in a joint American-Iraqi patrol was killed in Baghdad during fighting with insurgents, and a car bomb targeting a police checkpoint exploded in Baqouba, 35 miles northeast of Baghdad, killing another policeman, authorities said.

The international airport in Baghdad remained closed Tuesday after authorities shut it down 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.