A suicide bomber succeeded in killing 15 members of Iran's elite, and seemingly untouchable, Revolutionary Guard force last month.
The attack was carried out in the poverty stricken Sistan Baluchestan Province, and was the deadliest attack in the region in decades. Thirty-five civilians also perished.
Jundollah, a group which says it is fighting for the rights of the Baluch people, and thought to be hiding in neighbouring Pakistan, said it carried out the assault.
Now Nazanine Moshiri, Al Jazeera's correspondent in Iran, has been allowed to access the dangerous border area to investigate what lies behind the region's problems.
"Security is the main issue in Sistan Baluchestan," she said.
"I have travelled to that region twice now, and the fear there is kidnapping. Ambushes are common.
"But this [bombing] is a new tactic by Jundollah. It is something that happens in neighbouring countries, like Pakistan and Afghanistan, but not in Iran.
Poverty and drugs
"The other problem is drug-smuggling - a huge problem, with people coming across the border from Afghanistan. Iran is used as a trafficking route to Europe.
"And many think that the drug-smuggling is connected to Jundollah.
"Many feel the Revolutionary Guards could push hard, even going into Pakistan, to get Jundollah.
"But the other tactic is to win over the Baluchi-Sunnis to get them on to their side - by building roads and schools. Poverty is a big problem there. And you get a real sense that if security returns to this area, so will jobs.
"One local journalist told me that they should be talking to tribal leaders and that is the only way to win over the Baluchi-Sunnis."
Here is her report.
Source: Al Jazeera