Afghan officials say at least six people were killed and 22 wounded in a suicide car bombing in the capital, Kabul.
The attack occurred near the site of a planned meeting where thousands of Afghan political and tribal leaders will discuss a security agreement with the United States.
An agreement would let U.S. troops remain in Afghanistan after the final withdrawal of international combat troops at the end of 2014.
Officials say at least one soldier was killed in Saturday's attack, which targeted an Afghan army vehicle. Civilians were also among the casualties.
There was no immediate claim of responsibility.
Afghan and U.S. officials have been seeking to iron out a bilateral security pact that will help determine how many U.S. troops and bases remain in Afghanistan after 2014.