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Associated Press
In this photo released by the Syrian official news agency SANA, Arab league observers, right, icheck with a Syrian injured man who wounded during an explosion at Midan neighborhood in Damascus, Syria, on Friday Jan. 6, 2012. An explosion ripped through a police bus in the center of Syria's capital Friday, killing at least 10 people and possibly 25 in an attack authorities blamed on a suicide bomber, an official and state-run TV said. (AP Photo/SANA) EDITORIAL USE ONLY

BEIRUT — A bomb exploded Friday at a busy Damascus intersection, killing 26 people and wounding dozens in the second major attack in the Syrian capital in as many weeks, officials said, vowing to respond to further security threats with an "iron fist."

The government blamed "terrorists," saying a suicide bomber had blown himself up in the crowded Midan district. But the country's opposition demanded an independent investigation, accusing forces loyal to the Syrian regime of being behind the bombing to tarnish a 10-month-old uprising against President Bashar Assad.

"Is there anything worse than these crimes?" said Majida Jomaa, a 30-year-old housewife who ran to the streets after hearing the explosion. "Is this freedom?"

It was impossible to determine the exact target of the blast, but a police bus was riddled with shrapnel and blood was splattered on its seats, according to Syrian TV video and a government official. Blood also stained the street, which was littered with shattered glass.

The bomber "detonated himself with the aim of killing the largest number of people," Interior Minister Mohammed Shaar told reporters. State media said most of the dead were civilians but security forces were also among them.

Midan is one of several Damascus neighborhoods that have seen frequent anti-Assad protests on Fridays since the uprising began in March, inspired by the revolutions around the Arab world.

The violence marks a dramatic escalation of bloodshed in Syria as Arab League observers tour the country to investigate Assad's bloody crackdown on dissent. The monitoring mission will issue its first findings Sunday at a meeting in Cairo.

In a statement, the Interior Ministry vowed to respond to any security threats with an "iron fist."