"A savage and inhuman act" is how the Iranian military described Sunday's suicide bomb attack against its Revolutionary Guards in southern Iran.

At least 42 people were killed, and dozens more people were injured in the attack, in Pisheen in Baluchestan.

A number of senior officers were among the dead, including the deputy commander of the Guards' ground force.
 
According to Iranian state media, a Sunni group called Jundollah claimed responsibility for the attack. 
  
Mahmoud Ahmadinejad, the Iranian president, is alleging Pakistani involvement in the bombing, claiming that security agents in Pakistan have been working with terrorist groups across the border. 

But some Iranian officials have claimed Western powers were behind the bombing.
 
Just what's behind this escalation? With Iran quick to blame Britain and the US, how will this affect its relations with the West? Could this be another setback for diplomacy in the Iran nuclear impasse?

Inside Story presenter Maryam Nemazee is joined by Ghanbar Naderi, the political editor of the Iran Daily newspaper, Karim Sadjadpour, an associate at the Carnegie Endowment for International Peace, and Dan Plesch, the director of the Centre for International Studies and Diplomacy.

This episode of Inside Story aired from October 19, 2009.