The attack took place as al Qaeda in the Arabian Peninsula (AQAP) recruits queued for dinner at the camp, west of the port city of Mukalla on Yemen's south coast.
The Pentagon said on Tuesday that a US air strike on an AQAP training camp had killed dozens of fighters but it gave gave no further details.
The Yemeni sources said that at least 50 people were killed and 30 wounded. The air strikes set off huge fires inside the camp, residents said.
"The planes struck as al Qaeda people stood in line to receive their dinner meal," a local official, who asked not to be named, told Reuters by telephone.
Yemeni residents had earlier said the attack on the base was carried out by war planes from a Saudi-led coalition which over the past year had been trying to stop the Iran-allied Houthi group from completing its takeover of the country.
AQAP has exploited the war to expand its control in Yemen, seizing control of Mukalla, capital of Hadramout province, last year and recruiting more followers.
The US regards AQAP, formed by the merger of the Saudi and Yemeni wings of the group in 2009, as one of the deadliest branches of the network founded by Osama bin Laden.
The group had used Yemen to plot attacks against Western targets, including an attempt to bomb a US-bound airliner in 2009.
It also claimed responsibility for an attack on the Charlie Hebdo magazine in Paris that killed 12 people last year, although some analysts suspect its role was more inspirational than direct.
The US has frequently targeted al Qaeda militants across Yemen with drone strikes, killing many prominent leaders of the group over the past few years.
