* Group claimed a dual attack that killed at least eight
* Islamist group said "unintended defect" to blame
* Lebanon increasingly hit by spillover from Syria's war
BEIRUT, March 8 (Reuters) - A Sunni Lebanese militant group linked to al Qaeda has apologised for the civilian casualties of a suicide bombing last month and said its fight was against Iran and its ally Hezbollah, not Shi'ites in general.
The Abdullah Azzam Brigades took credit for a Feb. 19 attack on Shi'ite Iran's cultural centre in Beirut that killed eight people in an area where support for the Shi'ite political and military movement Hezbollah runs strong.
But in an unusual statement published on Islamist websites and on the group's Twitter feed, the group said it had intended the explosions to go off in an area where shrapnel would not reach the main street, so as to spare civilian lives.
"The Abdullah Azzam Brigades' operations do not target Shi'ites in general, or any other sect, and we always stress to our martydom-seekers to be cautious and abort an operation if they think it could kill others than those targeted," it said.
It blamed an "unintended defect" for the error.
Lebanon has been increasingly hit by violence linked to the war in its much larger neighbour Syria, which has killed over 140,000 people over the last three years and forced millions to flee their homes, including nearly 1 million into Lebanon.
The conflict has taken on an increasingly sectarian character. Hezbollah has sent fighters to assist President Bashar al-Assad, a member of the Shi'ite offshoot Alawite sect, while the rebels are overwhelmingly Sunni and include many hardline Islamists, including some linked to al Qaeda.
The Abdullah Azzam Brigades also claimed a November attack on the Iranian embassy in Beirut.
A group describing itself as the Lebanese branch of the Nusra Front, al Qaeda's affiliate in Syria, has also claimed suicide attacks in Shi'ite areas of Lebanon, including several in Beirut's southern suburbs.
The Abdullah Azzam Brigades said in its statement it chose only "legitimate targets" of Iran and Hezbollah, but also accused Hezbollah of using civilians as "human shields".
"We assure our people, the Sunni people and all Lebanon's sects: Our war is with the party of Iran and our targets are its interests and its military, security and political centres in Lebanon and abroad," it said, referring to Hezbollah.
(Reporting by Alexander Dziadosz and Omar Fahmy; Editing by Andrew Roche)