Islamabad  - Internet postings attributed to al-Qaeda claimed responsibility for this week's suicide car bombing at the Danish embassy in Islamabad that left six people dead.

The statement signed by Mustafa Abu al-Yazid, al-Qaeda's top leader in Afghanistan, and posted Wednesday on militant websites said Monday's attack was an act of revenge for "what the infidels from the so-called state of Denmark have published, the insulting cartoons of the Prophet Mohammed," according to a translation by the US-based SITE Intelligence Group Monitoring Service late Wednesday.

It added that the bombing was a warning to others.

"This should serve as a warning to the infidel countries regarding their crimes against our Prophet Mohammed," it said, according to SITE, which monitors terrorist content on websites. "They must apologize immediately or else this will only be the first step in our struggle."

The authenticity of the statement could not be determined.

The cartoons of Mohammed were first published in Danish and Norwegian newspapers in late 2005, triggering riots in early 2006 in several Muslim nations, including Pakistan.

The caricatures were reprinted on February 13 by Danish newspapers in defence of what they called freedom of speech after a plot to murder one of the cartoonists was uncovered. The publication retriggered protests.

On Monday, a single bomber blew up an explosives-laden car carrying fake diplomatic registration plates near the main entrance of the Danish embassy in the Pakistani capital. Among those killed were a Danish national of Pakistani origin and two of the embassy's local employees.

Pakistani Foreign Minister Shah Mehmood Qureshi condemned the attack. "There can be no justification for such an action," he said.

Danish Foreign Minister Per Stig Moller called the bombing "completely unacceptable" and suspected al-Qaeda of being behind the attack. (dpa)