Politicians from around the world have offered condolences to the family and friends of the victims of an attack on US embassy staff in Libya.

The US envoy to the North African country, Christopher Stevens, was killed along three others during a pro-Islamist riot broke in Benghazi on Tuesday night.

President Obama said in a statement that he strongly condemned "the outrageous attack".

He said the four victims "exemplified America's commitment to freedom, justice, and partnership with nations and people around the globe, and stand in stark contrast to those who callously took their lives.

"While the United States rejects efforts to denigrate the religious beliefs of others, we must all unequivocally oppose the kind of senseless violence that took the lives of these public servants."

"We are heartbroken by this terrible loss," added the US Secretary of State, Hillary Clinton.

"There are no words to express the shock and horror upon hearing the news of the murder," said Danny Ayalon, Israel's Deputy Minister of Foreign Affairs. "We extend our sympathies to his family, the U.S. Government and the American people."

"I received with astonishment and sorrow the news of the brutal attack against the US Embassy in Benghazi," wrote President Shimon Peres in a letter to his US counterpart. "The loss of life of four American citizens, including the US ambassador to Libya, Christopher Stevens, is a major pain and the citizens of Israel share with you."

Britain's Foreign Secretary, William Hague, said there could be no justification for the Benghazi riot. "It is essential that the Libyan authorities take urgent action to improve security, particularly in Benghazi, and identify those responsible for such attacks," he said.

"The UK stands ready to assist the Libyan authorities in any way we can and to support their efforts to continue the path towards a stable and secure Libya that fulfils the aspirations of the Libyan people."

Jewish groups have also expressed their sympathies with the families of the victims. "This attack, along with the attack on the US consulate in Cairo, Egypt hours earlier, is unacceptable," said B’nai B’rith International. "It should be condemned in the strongest words possible."

"Whether this murderous attack was premeditated or in reaction to a profoundly offensive anti-Islam film, nothing justifies the violence and killings of an innocent US diplomat and embassy personnel," added Abraham Foxman, national director of the Anti-Defamation League. "We strongly condemn the hateful anti-Islam message of the film. Still, it is not even clear that the attacks were prompted by the film, and we are deeply troubled at reports that the attacks on the embassies in Libya and Cairo may have been premeditated."