White House staff are pictured after they lowered the US flag to half staff on the roof of the White House in Washington Sept 12, 2012, following the death of US Ambassador to Libya, Chris Stevens and others in Benghazi. [Photo/Agencies]

BEIJING - The killing of the US ambassador to Libya has drawn from across the world condolences to the Americans and condemnation of violence against diplomatic missions.

US President Barack Obama on Wednesday denounced the deadly attack on the US consulate building in Libya's eastern city of Benghazi, vowing to bring the killers of Christopher Stevens and other three US diplomats to justice.

"The United States condemns in the strongest terms this outrageous and shocking attack," the president said in a statement delivered at the White House Rose Garden, with Secretary of State Hillary Clinton at his side.

"And make no mistake, we will work with the Libyan government to bring to justice the killers who attacked our people," he added.

The four Americans were killed when hundreds of protesters, angered by an alleged US-made movie that insults Prophet Mohammed, stormed and set ablaze the US consulate building on Tuesday night.

Stevens, who was on a short trip to Benghazi, died from suffocation as a result of smoke inhalation, the pan-Arab Al-Jazeera TV reported Wednesday.

UN Secretary-General Ban Ki-moon and the UN Security Council also condemned the deadly attack "in the strongest terms".

"The United Nations rejects defamation of religion in all forms," Ban said in the statement. "At the same time, nothing justifies the brutal violence which occurred in Benghazi yesterday."

Other senior UN officials also voiced their strong condemnation, saying that the "horrific and tragic attack" further highlighted the security challenges facing the authorities in the North African country.

European Union foreign policy chief Catherine Ashton deplored the killing "in the strongest possible terms", expressing sympathy to the families of the victims and the US authorities.

She urged Libya to "take all necessary measures without delay" to protect the lives of all diplomats and foreign staff working in the country and to "work tirelessly to bring those responsible for these killings to justice".

Moscow condemned the attacks against US diplomatic missions in Egypt and Libya, expressing its deep concern over the violence in the two Arab countries.

Russia strongly condemned the attacks against diplomats and diplomatic missions and took them as acts of terrorism, the Foreign Ministry said in a statement.

French President Francois Hollande firmly condemned the attack, calling on "Libyan authorities to shed light on these odious and unacceptable crimes, identify those culprits and bring them to justice." He affirmed France's solidarity with the United States.

NATO Secretary General Anders Fogh Rasmussen strongly slammed the attack, saying "such violence can never be justified".

"I welcome the Libyan president's condemnation and condolences and his pledge of his government's full cooperation. It is important that the new Libya continues to move towards a peaceful, secure and democratic future," he said in a statement.