KANDAHAR (Reuters) A powerful car bomb exploded outside a Nato base in Afghanistans southern Kandahar city on Wednesday, destroying scores of vehicles but causing no casualties, officials said. The blast was the latest in a string of attacks in Kandahar in recent months as militants step up their campaign of violence ahead of a major US-led offensive due to begin in the coming weeks aimed at driving the Taliban from their spiritual home. The bomb, which had been placed inside a parked vehicle in a parking lot, exploded around noon local time, destroying 11 cars and 50 motorbikes, the Interior Ministry said in a statement. Witnesses said they saw smoke and dust rising into the air above the city. Fortunately, there were no casualties caused by this explosion, the Interior Ministry said. A spokesman for Nato-led forces in Kabul said the explosion happened just outside the gates of Camp Nathan Smith, a NATO base inside the city, but said there were no foreign troop casualties. The base is home to the Canadian Provincial Reconstruction Team (PRT), a military-led effort for development in the area. Nato forces are planning the biggest military offensive of the nearly nine-year-old war in coming months in and around Kandahar, the biggest city in the south and heartland of the Taliban movement.