Two mid-level al-Qa'ida leaders were killed in Yemen, Osama bin Laden's ancestral homeland today, the defence ministry said.
Residents said they saw a drone in the air at the time.
The Yemeni defence ministry identified the men as two brothers, Musa'id and Abdullah Mubarak, and said they were killed at around dawn in the remote province of Shabwa, where a Yemen-based wing of al-Qa'ida is active.
It was not yet clear who carried out the attack and why they were targeted at this time.
Some nearby residents said they saw a drone in the air at the time of the killing while others reported seeing a rocket followed by an explosion on the ground.
The attack follows the killing of bin Laden by US forces in Pakistan on Monday and took place as Yemen is gripped by a standoff between President Ali Abdullah Saleh and a protest movement bent on his overthrow.
The United States and neighbouring Saudi Arabia want the crisis resolved, fearing a protracted standoff could lead to clashes between rival military units and igniting chaos across the country that al-Qa'ida could exploit.
Al-Qa'ida's Yemen branch, formed from the 2009 merger of the group's Yemeni and Saudi wings, has vowed to bleed US resources with small, cheap attacks that force the West to spend billions of dollars to guard against.
It tried but failed to kill Saudi Arabia's security chief in 2009 and claimed responsibility for a foiled attempt the same year to blow up a Detroit-bound plane. It was also blamed for bombs found in cargo en route to the United States in 2010.
Yemen, a US ally against al-Qa'ida, declared open war on the Yemen-based arm in January 2010, stepping up air strikes in which civilians as well as militants were killed.
A US diplomatic cable leaked in November said the United States was carrying out air raids on al-Qa'ida targets in Yemen, and that Saleh agreed to conceal this from the public.