Two rockets hit a residential area in the north of the Afghan capital, Kabul, late on Sunday.
US troops are involved in a major operation against Taleban fighters
They landed several kilometres from the site where hundreds of delegates at the loya jirga (grand council) are debating Afghanistan's new constitution.
A house was damaged in the attack, but there were no injuries.
The authorities in Kabul and Nato-led peacekeeping forces say remnants of the former Taleban want to disrupt the historic meeting.
On Sunday, the new US commander in Afghanistan outlined a major change of strategy to improve security in areas where Taleban guerrillas continue to operate.
General David Barno said US bases would be set up in the south-east, where the violence has forced international aid agencies to pull out.
He said the move would also open the way for landmark elections next year.
The loya jirga is forging Afghanistan's political future
His comment came as the loya jirga appeared to have made progress on agreeing key constitutional issues.
Delegates reportedly agreed in principle to back a strong presidential system supported by Afghan interim President Hamid Karzai.
The spate of recent attacks has forced the UN and other relief agencies to leave some areas, seriously affecting aid delivery.
The attacks have also threatened to undermine the reconstruction efforts by the US-backed Afghan Government.
General Barno said that by March next year there would be at least 12 civilian-military units - Provisional Reconstruction Teams (PRT) - operating in Afghanistan, including deployments in the troubled regions of Zabul and Oruzgan.
So far, the nine PRT units have been operating in relatively secure regions of Afghanistan.
On Saturday, the US envoy to Afghanistan, Zalmay Khalilzad, said it appeared that President Karzai was winning support for the controversial presidential system after a week of debates at the loya jirga.