A United States drone strike killed two suspected members of al-Qaeda in southern Yemen, said a security official and residents.

Saturday's raid in Ahwar, in the southern province of Abyan, killed two suspected fighters on a motorbike, the security official said.

It came after two days of intensive air strikes by US warplanes on fighters in the war-torn country.

Tribal sources and residents said another drone fired at a crowd of suspected al-Qaeda fighters in al-Saeed, in the adjacent province of Shabwa, but there were no reports on casualties in that incident.

On Friday, the Pentagon said it carried out "somewhere over 30" strikes against al-Qaeda in the Arabian Peninsula (AQAP) in two days, conducted in partnership with the Yemeni government.

"This is part of a plan to go after this very real threat and ensure that they are defeated and denied the opportunity to plot and carry out terrorist attacks from ungoverned spaces," Pentagon spokesman Navy Captain Jeff Davis said on Friday, noting the US would continue to attack AQAP.

Yemeni officials and tribal sources said at least 20 fighters were killed in the air strikes on Thursday and Friday in the southern provinces of Abyan and Shabwa and the nearby central province of Baida.

The increased bombing comes a little more than a month after a botched American raid against AQAP left a number of civilians and a US Navy SEAL dead.

Yemen has been torn apart by conflict since 2014, when Houthi rebels, allied with troops loyal to former President Ali Abdullah Saleh, captured large expanses of the country, including the capital Sanaa.

A coalition of Arab countries assembled by Saudi Arabia launched an air campaign against the rebels in March 2015.

Seven ceasefire accords have failed to end the war, which has left more than 7,500 dead and 40,000 people wounded, according to UN tally.