US fighter jets have carried out dozens of air raids on suspected al-Qaeda positions in southern Yemen for a second consecutive day, according to the Pentagon and sources on the ground.

The overnight operation on Friday included another assault in the Wadi Yashbum village in Shabwa province, where residents told the Reuters news agency that some of the strikes had hit civilian homes and a number of civilians were among the wounded.

The air raids also struck the home of al-Qaeda's commander in the area, Saad Atef, tribal sources told the AFP news agency.

Security officials in the area told AFP that eight suspected al-Qaeda fighters were killed in the strikes.

Tribal sources also said that women and children were wounded in the air raids, which came a day after the Pentagon confirmed carrying out more than 20 strikes in the Shabwa, Abyan and al-Bayda provinces.

Residents and local officials said at least 12 suspected al-Qaeda fighters were killed in Thursday's strikes.

Reports of ground battles

In addition to Friday's air raids, residents reported two separate gun battles between US ground troops and al-Qaeda fighters overnight, according to Reuters.

Backed by drones and Apache helicopter, the troops descended on Wadi Yashbum midnight and engaged suspected al-Qaeda fighters in a battle that lasted nearly half an hour, residents said.

The second half-hour battle came three hours later in the Jabal Mugan area of neighbouring Abyan province, according to residents, who also reported air raids.

Later on Friday, the Pentagon confirmed Friday's new wave of air strikes but denied reports that US forces had been engaged in ground combat or conducting raids.

"I know there have been reports of firefights, raids, there have not been any that US forces have been involved in [on Friday]," Navy Captain Jeff Davis, a Pentagon spokesman, told reporters.

He added that since Thursday there had been about 30 US air raids in total against al-Qaeda's Yemen branch.

Adam Baron, visiting fellow at the Europe Council on Foreign Relations in Beirut, said the US was trying to assert its authority in Yemen.

"What you have here over the past 24 hours is the US military launching a series of strikes in a way that does appear to be a strong action against al-Qaeda, even if the ultimate results of these strikes remain unclear," he told Al Jazeera.

"It looks like they're basically aiming to bombard various areas that are known as so-called strongholds of al-Qaeda and their backers. That being said, there is obviously a huge possibility of civilians being caught in the crossfire," Baron added.

"So, there is a huge danger that, even if you are hitting al-Qaeda targets, that civilians will be caught in the crossfire, which risks blowback beyond being a violation of international humanitarian law."

READ MORE: Key facts about the war in Yemen

The latest operations come a month after a January 29 raid on al-Bayda that residents said killed 16 civilians as well as al-Qaeda fighters.

The operation, the first of its kind authorised by President Donald Trump, was hailed as a success by the White House and other US officials.

But critics questioned the value and effectiveness of the mission since it killed women and children, as well as Navy SEAL Ryan Owens.

Owens's father has described the mission as "stupid", and declined to meet Trump.

Al-Qaeda has exploited a power vacuum created by two years of war between Yemen's government and Houthi rebels who control the capital to consolidate its presence, particularly in the south and east.

Successive US administrations have kept up a drone war against al-Qaeda's Yemen branch since soon after the September 11, 2001 attacks.