KANDAHAR, Afghanistan - Three persons were killed and seven others wounded as a blast rocked the electioneering office of President Mohammad Ashraf Ghani in the Kandahar city, the capital of southern Kandahar province on Tuesday, provincial police spokesman Jamal Barikzai said Wednesday.

According to Barikzai, an explosive device was planted at the wall of the campaign office, went off Tuesday evening, killing three people including a child and a woman and injuring seven others including a woman.

The presidential office has yet to make comments.

Without providing more details, the official said that investigation had been initiated into the incident.

Wednesday is the last day of the election campaign for the Sept 28 presidential elections and Ghani is a leading candidate in the race.

This is the second attack on Ghani's election campaign over the past one week. In the previous attack, which occurred in Charikar city, 55 km north of Kabul on Sept 17, 26 persons were dead and 42 others injured.