KABUL, Afghanistan - Armed assailants abducted a German woman from a restaurant in Kabul on Saturday, officials said, prompting police to shoot at the speeding getaway car, killing a nearby taxi driver. A Taliban spokesman, meanwhile, said negotiations for 19 South Korean hostages held since July have failed.

And in southern Afghanistan, a suicide car bomber targeting a security forces convoy killed 15 people.

In Saturday's abduction in Kabul, the armed men pulled up next to a barbecue and fast food restaurant, and one of the men went inside the restaurant and asked to order a pizza, said intelligence officials investigating the kidnapping. Two assailants waited outside, while another waited in a parked gray Toyota Corolla.

The man in the restaurant then pulled out a pistol, walked up to a table where the woman was sitting with her boyfriend, and took her from the restaurant, the officials said on condition of anonymity because of policy. It was not immediately clear what happened to the boyfriend.

Police in the area, alerted to the kidnapping, spotted the speeding car. They opened fire, but the bullets instead hit a nearby taxi and killed its driver.

Julia Gross, spokeswoman for the German Foreign Ministry in Berlin, said German officials were "pursuing reports of a possible kidnapping of a German citizen."

U.N. staff in Kabul, meanwhile, were told Saturday afternoon to remain in their locations as authorities investigated the abduction, a U.N. official said on condition of anonymity because he was not authorized to speak on security matters. Other foreigners were also placed under tight security.

Many foreigners live in the neighborhood, including families with children attending the international school nearby.

The latest kidnapping comes amid heightened fears of abductions, after 23 South Koreans and two Germans were taken hostage in separate incidents last month in central Afghanistan.

One of the German men has been shot to death, and the other remains captive.

Taliban militants killed two of the South Koreans and released two after face-to-face talks with South Korean officials.

Qari Yousef Ahmadi, a Taliban spokesman, said the group's demands for the release of the remaining 19 South Koreans remains the same -- a swap for Taliban prisoners, which the Afghan government has ruled out.

"That's why from our side, we say the negotiations have failed, but we're still ready for more negotiations if the Korean side is willing to meet our demands ... the exchange of prisoners," he said by telephone from an undisclosed location.

In southern Afghanistan, a suicide car bomber detonated near a convoy of private security forces, killing four Afghan guards and 11 civilians, including women and children, police said.

The suicide car bombing went off west of Kandahar city and also wounded six other guards as well as 20 civilians who were in two minivans passing by the convoy, Kandahar provincial police chief Syed Agha Saqib said.

Three women and two children died in the blast, and five women and three children were among the civilians wounded. Women's and children's shoes were scattered about the area. A stuffed animal toy was left in one of the destroyed minivans.

Saqib said the guards worked for U.S. Protection and Investigations security firm. Company representatives could not immediately be reached to confirm that their employees were attacked.

In neighboring Helmand province, insurgents holed up in buildings and trenches attacked Afghan police and coalition forces Friday near Fire Base Robinson, the coalition said in a statement. Nearly a dozen suspected militants were killed in the ensuing battle.

It was the third insurgent attack on the joint forces in as many days, the statement said. No Afghan or coalition forces were wounded in the three days of fighting.

Since early spring, Afghan and international forces have been battling insurgents in Helmand -- scene of some of the heaviest fighting over the last two years and the largest opium poppy-growing region in the world.

Violence in Afghanistan has risen sharply during the last two months. More than 3,700 people have died so far this year, most of them militants, according to an Associated Press tally of casualty figures provided by Western and Afghan officials.