(CNN) -- More violence from suspected al Qaeda militants in Yemen continued Sunday in two separate attacks.
At least 13 Yemeni soldiers were killed and nine others were injured when the militants ambushed a military police headquarters in the southern Yemeni province of Hadramout, two Interior Ministry officials told CNN. The attackers "easily escaped," said Ali BaNajjar, who witnessed the ambush in Hadramout.
A second attack occurred close to a checkpoint near the Yemeni presidential palace in the capital, Sanaa, according the government officials. Several militants were killed, said Mohammed al-Qayedi, a spokesman for the Interior Ministry.
It's not the first time militants have targeted Sanaa security forces. On Friday, nearly 20 gunmen attacked the political security headquarters in the capital and killed four troops and injured at least four others at a checkpoint. Three attackers were killed, while the others fled unharmed.
The violence seems in line with a promise a senior al Qaeda operative made last week -- that the organization was going to bring bloodshed to Sanaa.
Al Qaeda appears to be making good on its threat, one Yemen-based analyst told CNN.
"After al Qaeda threatened to move the fight to the main cities, attacks against foreigners and Yemeni forces in Sanaa more than tripled compar(ed) to a month before," said AbdulSalam Mohammed, president of the Sanaa-based Abaad Strategic Center. "Troops need to be on high alert if they have a chance to defeat the militants."
The Defense Ministry Sunday said that tens of al-Qaeda militants were killed over the last two days, among them many foreign fighters.
On Saturday, CNN reported that a Yemeni government official said two al Qaeda gunmen tried to kidnap two U.S. Embassy workers on April 24.
The attackers were part of the terrorist group al Qaeda in the Arabian Peninsula, or AQAP, the official said. The shooting that stopped them happened near a Yemeni barbershop "where many foreigners and diplomats go to get their hair cut," the Yemeni official said.
Of all al Qaeda-affiliated networks worldwide, AQAP is considered the most dangerous threat to Americans.
The two U.S. Embassy personnel were apparently not supposed to be near the barbershop, the official said.
"These individuals violated security protocol," the Yemeni official said. "U.S. Embassy personnel are not allowed to leave their secure facilities. The American who shot the kidnappers had a gun permit and was authorized to carry a gun. The two armed kidnappers were AQAP militants. They weren't unarmed civilians."
Marie Harf, deputy spokeswoman for the U.S. State Department, confirmed the incident in a statement.
"Two U.S. Embassy officers in Yemen fired their weapons after being confronted by armed individuals in an attempted kidnapping at a small commercial business in Sanaa," the statement read. "Two of the armed individuals were killed. The Embassy officers are no longer in Yemen."
The revelation of the incident comes after the U.S. Embassy in Yemen was closed indefinitely Wednesday amid security concerns and as fighting between security forces and AQAP intensified.
Just days before the abduction attempt, a joint U.S.-Yemeni operation was being carried out against AQAP in the Abyan and Shabwa regions of Yemen. Authorities did not disclose whether drones were used in the strikes. The use of the unmanned drones has stirred controversy because the drones have killed civilians, a high-level Yemeni official has said.
A top Yemeni Interior Ministry official said the U.S. government had considered closing the embassy two weeks ago, as attacks on foreigners intensified.
The violence near the barbershop, and violence against other foreigners in the past six weeks, persuaded Americans to close down the U.S. Embassy this past week, the official said.
Hakim Almasmari reported from Yemen. CNN's Elise Labott contributed to this report.