Though Iran has yet to confirm the attack, the terror group Ansar al-Furqan Ahwaz Martyrs Brigade claimed responsibility in an official statement, which noted "This operation was conducted to inflict losses on the economy of the criminal Iranian regime." Ansar al-Furqan is a relatively new group, having been founded in 2013, and has ties to Syria's Al-Qaeda-linked Al-Nusra Front (currently called Ha'yat Tahrir al-Sham). It is comprised primarily of Baluchi Salafist militants which are hostile to the Iranian government - the Baluch people, an entho-linguistic group, are spread primarily throughout southern Iran, Afghanistan, and western Pakistan.
Both the video and written statement identify the location of the attack as near near Omidiyeh, a city in Khuzestan Province - an area of the country which has witnessed periodic uprisings and sporadic bombings going back to 1979 and into the mid-2000's.
According to the AP, this constitutes the first such attack by this particular group:
SITE [the U.S.-based SITE Intelligence Group] says the attack by Ansar al-Furqan, if confirmed, would be their first in oil-rich southern Iran.