A group of suicide bombers caused heavy casualties in the capital of Afghanistan\'s southwestern Nimroz province on the border with Iran, officials said Tuesday. \"We have confirmation that 21 civilians and 15 members of the security forces have been killed in these attacks and more than 66 others injured,\" provincial governor Abdul Karim Brahawi told AFP, while the deputy police chief said there were \"heavy casualties\". The summer offensive by militants in Afghanistan is a sadly expected feature. This year the Taliban specifically threatened those working for foreign security companies and there have been several instances of executions of contractors. July was the most violent month in Afghanistan for two years amid fears that American and NATO  withdrawal from Afghanistan will leave an incapable, underfunded and under equipped Afghan army to protect the country.