Al Jazeera's Hamish MacDonald reports on Saturday's suicide attack on a US military convoy in Kabul. It is six years since US forces arrived in Afghanistan, but signs abound that the Taliban is fighting back. At 8.15 on Saturday morning occurred the latest strike - a suicide bomber drove directly into a US convoy. This is the already the most violent year this country has seen since the fall of the Taliban. It claims this attack is the thirteenth suicide bombing carried out during Ramadan. At least four vehicles were destroyed and again, women and children were among the casualties. US and Nato soldiers secured the scene as the wounded were taken to hospital. Government officials have condemned the violence, but once again the Taliban is warning more bombings should be expected by the end of Ramadan.