"Successful counter-terrorism operations conducted by government of Yemen security forces January 4 north of the capital have addressed a specific area of concern, and have contributed to the embassy's decision to resume operations," the US embassy said in a statement.
The British and French embassies, which had also been closed, resumed operations but remained closed to the public, diplomats at those embassies said.
Hakim al-Masmari, the editor of the Yemen Post newspaper in Sanaa, told Al Jazeera: "The operations started two days ago. Our sources said that the government has sent over 10,000 troops there.
"They are trying to force tribesmen there to make them understand that those who talk or help al-Qaeda leaders or members will be faced in a very severe manner."
Concerning the two people killed in raids on Monday, al-Masmari said: "Our sources say that they have no links to al-Qaeda whatsoever.
"No matter what the government says there is no proof whatsoever that they are al-Qaeda or have any links to them at all."
Al-Masmari said that the US and UK were not involved in any of the actions against suspected al-Qaeda fighters, except in providing intelligence information to Sanaa.
International focus has shifted to Yemen in the wake of an attempted bombing of a US-bound airplane on Christmas Day.
Al-Qaeda in the Arabian Peninsula claimed responsibility for the attempted attack and Barack Obama, the US president, said that the man accused of trying to ignite explosives as it arrived in Detroit had received his training and explosives in Yemen.
Hillary Clinton, the US secretary of state, said on Monday that Yemen posed a global threat and offered support for the country's security forces.
"Obviously, we see global implications from the war in Yemen and the ongoing efforts by al-Qaeda in Yemen to use it as a base for terrorist attacks far beyond the region," she said.
Clinton praised the Yemeni government for its efforts to combat al-Qaeda in Yemen, but said it was "time for the international community to make it clear to Yemen that there are expectations and conditions on our continuing support for the government".
Her comments sparked debate over the nature of US intervention in Yemen.
Earlier Abu Baker al-Qirbi, Yemen's foreign minister, made clear that while Yemen was happy to received "development assistance", any military intervention by the US would cause more harm than good.
"Yemen is going to deal with terrorism in its own way, out of its own interests and therefore I don't think it will counter-fire," he told Al Jazeera, ahead of Clinton's comments to the media.
As well as the threat from al-Qaeda in the Arabain Peninsula, Yemen is currently battling Shia Houthi fighters in the north, as well as a secessionist movement in the south.
Analysts have warned against direct US intervention in Yemen.
Mark Perry, a Washington-based independent military and foreign policy analyst, said Clinton needed to approach the situation more diplomatically.
"The escalation in the rhetoric seems to have happened overnight," told Al Jazeera.
"Hillary Clinton has looked in her toolbox and pulled out a lecture for the Yemeni government that they have to do something and do something now because a single airplane on American tarmac with an unsuccessful bomber has made Yemen an international threat."
He said that while Yemen has become "increasingly destabilised", al-Qaeda, whose affiliate in Yemen, al-Qaeda in the Arabian Peninsula, combines both Yemen and Saudi fighters, was far from the major reason for the instability.
"You need to turn the environment against them [al-Qaeda], you need to make the environment against their beliefs and ideology"
founder of Institute for Near East and Gulf Military Analysis
"The Houthi rebellion in the north is the key issue here and it can only be solved diplomatically. We're not going to go into Yemen with the 10th Mountain division or the 82nd Airborne and help the Yemenis in their own country. We're only going to destabilise if we do that," he said.
"This is the time for Hillary Clinton to stop lecturing and start working on diplomacy."
Riad Kahwaji, the founder of the Institute for Near East and Gulf Military Analysis in Dubai, said any engagement in Yemen needed to be seen as a long-term strategy.
"Al-Qaeda in Yemen are Yemenis, they're not foreign fighters ... They have sympathy and support from tribal leaders in parts of Yemen, which is enabling them to move around and function freely," told Al Jazeera.
"You need to turn the environment against them, you need to make the environment against their beliefs and ideology, otherwise military strikes will have very limited results."