Meanwhile, Iraqi authorities announced a shortening of the capital's overnight curfew, calling it a sign that an intensive security crackdown in Baghdad by U.S. and Iraqi troops is yielding results.

The city's residents will now have to stay indoors between 10 p.m. and 5 a.m., instead of between 8 p.m. and 6 a.m.

Word of the shortened curfew came hours after the kidnappers of German nationals Hannelore Krause, 61, and her 20-year-old son Sinan posted a video on the Internet in which they displayed the hostages anew and set what they said was a 10-day deadline for Germany to agree to withdraw troops from Afghanistan.

"You don't know what we are going through," a sobbing Krause, clad in a head scarf and black robe, said in German on the 5 1/2-minute videotape. "I'm so scared -- we have just a couple of days. ... Do something!" Her son cried along with her.

Krause, who is married to an Iraqi doctor and has lived in Baghdad for years, was seized from her home Feb. 6, together with her son. She works for the Austrian Embassy in Baghdad, and her son, a dual Iraqi-German national, is employed by the Iraqi foreign ministry.

The kidnappers are a previously unknown Islamist group calling themselves the Brigades of the Arrows of Righteousness.

Germany has no troops in Iraq, but does have 30,000 soldiers in Afghanistan as part of the NATO-led force.

Abductions are commonplace in Iraq, targeting both foreigners and vastly larger numbers of Iraqis. Sometimes the kidnappers are insurgents, sometimes they are criminal gangs seeking ransom.

About 400 foreigners have been abducted during the 4-year-old war, and thousands of Iraqis have been seized.

In the northern city of Kirkuk, residents Tuesday salvaged belongings from dozens of buildings damaged or destroyed by a powerful truck bomb that killed up to 15 people and injured about 150 others.

A U.S. soldier died of wounds suffered in the blast, the U.S. military announced late Monday. Many of the wounded and at least one of the dead were pupils from a nearby girls' primary school.

The deaths of another three U.S. soldiers in Anbar province were announced late Monday, the same day a Republican congressional delegation, including Arizona Sen. John McCain, visited the restive area west of Baghdad.

In Shorja market -- where McCain and three other congressional Republicans went Sunday for one hour -- most shops were shuttered Tuesday by 2:30 p.m. They included the carpet shops where Sen. Lindsey Graham, R-S.C., said he bought "five rugs for five bucks."

Thin crowds walked the street, which was fortified by concrete barriers and razor wire. Iraqi soldiers in a Humvee were positioned at one end of the street.

But merchants on Tuesday said they fear for their lives, despite the drop in killings in Baghdad last month reflected in the morgue data.

Chronicle news services contributed to this report.

This article appeared on page A - 3 of the San Francisco Chronicle