Thursday's first reported drone attack hit a car carrying suspected militants in the district of Wadi Ubaidah, about 175 kilometers (109 miles) east of Sanaa, and killed six, a security official said.
Badly burned bodies lay beside their vehicle, according to the official. Five of the dead were Yemenis, while the sixth was believed to be of another Arab nationality, he said.
The second drone attack killed three alleged militants in the al-Ayoon area of Hadramawt province in the south, the official said. The third, also in Hadramawt province, killed three more suspected militants in the al-Qutn area, he added.
All the airstrikes targeted cars, added the official, who spoke on condition of anonymity because he was not authorized to talk to the media.
The drone strikes have become a near-daily routine since they began July 27. So far, they have been concentrated in remote, mountainous areas where al-Qaida's top five leaders are believed to have taken refuge.
But drones also have been seen and heard buzzing for hours over Sanaa, worrying residents who fear getting caught in the crossfire.
While the United States acknowledges its drone program in Yemen, it does not talk about individual strikes or release information on how many are carried out. The program is run by the Pentagon's Joint Special Operations Command and the CIA, with the military flying its drones out of Djibouti, and the CIA out of a base in Saudi Arabia.
Pentagon spokesman Army Lt. Col. Todd Breassale declined to comment Thursday and would not confirm the existence of a military drone program in Yemen. The CIA also declined to comment.
Since July 27, drone attacks have killed 34 suspected militants, according to an Associated Press count based on information provided by Yemeni security officials.
The terror network's Yemeni offshoot bolstered its operations in Yemen more than a decade after key Saudi operatives fled here following a major crackdown in their homeland. The drone strikes and a U.S.-backed offensive that began in June 2012 have driven militants from towns and large swaths of land they had seized a year earlier, during Yemen's political turmoil amid the Arab Spring.
The sudden drone barrage could further upset a population already angered by bombings that have killed civilians, said Gregory Johnsen, the author of "The Last Refuge: Yemen, al-Qaida and America's War in Arabia."
"It's a really rapid increase when there was a long time where there were no drone strikes for weeks," Johnsen said in an interview with the AP. "This has a lot of people in Yemen on edge."
A U.S. intelligence official and a Mideast diplomat have told the AP that the embassy closures were triggered by the interception of a secret message between al-Qaida chief Ayman al-Zawahri and Nasser al-Wahishi, the leader of the Yemen-based offshoot, about plans for a major attack.
Authorities in Yemen said they had discovered al-Qaida plot to target foreign embassies in Sanaa and international shipping in the Red Sea.
Yemeni authorities said this week that a group of al-Qaida militants have entered Sanaa and other cities to carry attacks. It issued list of 25 al-Qaida wanted militants. The Yemeni statement said security forces will pay $23,000 to anyone who comes forward with information that leads to the arrests of any of the wanted men.
The discovery of the al-Qaida plot prompted the Defense Ministry to step up security around the strategic Bab el-Mandeb waterway, which connects the Red Sea with the Gulf of Aden. Officials banning speedboats or fishing vessels from the area.
Details of the plot were reminiscent of the suicide attack on the USS Cole in 2000 in Aden harbor that killed 17 American sailors.
One local political analyst suggests the latest plots were floated by the group to show it is still a formidable force.
"Al-Qaida has suffered losses and it is trying to make an impression," said analyst Ali al-Sarari, who is close to the Yemeni government. "The mere talk about an upcoming attack gives the group a chance to restore its shattered image ... as a group capable of exporting terrorism."
A senior security official told AP that the al-Qaida leaders never meet together out of fear of a drone attack killing all of them at once. These include al-Wahishi, a onetime aide to Osama bin Laden; Qassem al-Raimi, believed to be the military commander; and Ibrahim al-Asiri.
The official, who spoke on condition of anonymity because he is not authorized to brief the media, said al-Wahishi is believed to be trying to recruit informants in the mountainous areas of Marib in central Yemen, especially in the Wadi Ubaidah valley, where tribal allies of ousted President Ali Abdullah Saleh are concentrated.
Abed Rabbo Mansour Hadi became president in 2012 after a year of mass protests demanding Saleh's ouster. Since then, Hadi has accused Saleh's men, who are still in key positions in security agencies and municipalities, of trying to hinder his reforms.
Marib is one of the few places known to be al-Qaida strongholds, and the Yemeni military has not tried to carry out a large offensive there because of the strong presence of anti-government tribes.
The official said al-Raimi is believed to be moving in southern Yemen, while al-Asiri is believed to be in the north, close to the border with Saudi Arabia, his home.
Johnsen said the U.S. faces a major problem in Yemen when it comes to intelligence gathered on the ground. By relying solely on cellphone calls and other intercepts, chances are increased that a drone strike could merely target a tribesmen who once called an al-Qaida figure, rather than a militant, he said.
"The U.S. is firing missiles into a country, if not blindly, maybe just one-eyed." he added.
Yemeni troops have stepped up security across Sanaa, with multiple checkpoints set up and tanks and other military vehicles guarding vital institutions. The army has surrounded foreign installations, government offices and the airport with tanks and troops.
In Sanaa's cafes and on its public transportation, the drones were a popular topic of conversation, prompting fear and even some dark humor.
"These aircraft are really scaring people here," said Mohammed al-Mohandis, a teacher, who added that he and his friends heard the drone while chewing leaves of qat, the mild stimulant plant that is addictively used in Yemen.
Al-Mohandis even joked with his buddies that someone could have planted an electronic chip on them. "Watch out, or you are finished!" he said, drawing laughter.
Another Sanaa resident, Ahmed Said, suggested the Americans should target those who cause power outages in the city, instead of al-Qaida.
Speaking to AP over the phone, Said shouted at a man crossing the street slowly: "Hurry up, the drone will hit you!"