By Hamid Shalizi

KABUL (Reuters) - A teenaged bomber on Thursday targeted a Kabul auditorium packed with people watching a drama condemning suicide attacks and being staged at a French cultural center, killing a German man and wounding 16 people, officials and a witness said.

The suicide blast was the second to strike the Afghan capital in a day, after six Afghan soldiers perished when their bus was hit on the outskirts of the city as they rode into work.

The violence, part of a nationwide campaign by Islamist Taliban insurgents to strike at military and civilian targets, came less than three weeks before the year-end deadline for most foreign combat soldiers to withdraw from the country.

General Ayoub Salangi, head of the Interior Ministry while the cabinet is being finalised, said the suspected theater bomber appeared to have been about 17 years old and detonated his explosives at the venue during an early evening performance.

"I heard a deafening explosion ... There were Afghans, foreigners, young girls and young boys watching the show," Sher Ahmad, an Afghan rights activist who was at the performance, told Reuters.

He said the blast came during a performance of a new play called "Heartbeat: Silence After the Explosion", a condemnation of suicide attacks.

"Pieces of flesh were plastered on the wall. There were children and women crying for help. Some were running out, some were just screaming."

Taliban spokesman Zabihullah Mujahid said the bomber targeted the event because it was staged "to insult Islamic values and spread propaganda about our jihad operations, especially on suicide attacks".

Amid confusion immediately following the blast, one person could be heard saying "It's all part of the show" in a video posted on YouTube purporting to be of the attack.

HEAVY SECURITY

Early police reports said the bomber attacked the French-run Lycée Esteqlal, one of Kabul's oldest and most highly respected high schools, but Ahmad said the performance was at the French Cultural Centre located in the same compound.

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Salangi said the person confirmed killed was a German man, but he could not immediately confirm his identity.

German Foreign Minister Frank-Walter Steinmeier said the attack was "particularly perfidious because it ... was against exactly those people who are helping the country to build a better future."

The French government said in a statement that "several" people were killed in the attack and "many" more injured, but none of the fatalities were French nationals.

The venue was heavily guarded during the event, according to Kabul police chief Abdul Rahman Rahimi, who added that the bomber may have hidden explosives in his underwear to pass through security.

He said the bomber detonated the explosives at the top of the auditorium stairs, which may have prevented more casualties. The body of the bomber was shredded, but police were able to identify him as a teenager because his head was found intact.

Taliban militants have stepped up a campaign of violence this year to take advantage of uncertainty and weakness besetting Afghanistan's security forces as they prepare to take over the war on the insurgency, now in its 13th year.

Earlier on Thursday, a suicide bomber targeted a bus carrying Afghan army personnel, the Defense Ministry said, ending a near two-week lull in attacks in the capital. As well as the six soldiers killed, 11 were wounded.

Five Afghan school children were also reported killed in a foreign forces air strike in northern Parwan province, Afghan officials said.

The International Security Assistance Force confirmed an air strike in the area, but said five insurgents were killed.

Civilian casualties caused by air strikes have been one of the most contentious issues of the war, although there are often conflicting claims.

(Additional reporting by John Irish in PARIS; Writing by Kay Johnson; Editing by Mike Collett-White)