(CNN) -- Reaction to a brazen attack at Nairobi's Westgate Mall that left dozens dead and hundreds more wounded poured in Saturday from around the world, with leaders condemning the killings and pledging support to Kenya:
Secretary-General Ban Ki-moon "is following closely and with alarm" the developments and is being regularly briefed by his senior advisers, according to a written statement released by the United Nations press office.
Ban spoke with Kenya's president about the attack, it said.
"He also offered his solidarity as the Kenyan authorities handle the incident," the statement said.
The United States has offered its full support to the Kenyan government to bring to justice those responsible for "this heinous act," according to a statement released by the White House.
"We will continue to stand with the Kenyan people in their efforts to confront terrorism in all its forms, including the threat posed by Al-Shabaab," National Security Council spokeswoman Caitlin Hayden said, according to the statement.
"This cowardly act against innocent civilians will not shake our resolve."
The Obama administration also extended its condolences to the families of those killed and injured, including a number of U.S. citizens hurt in the attack, the statement said.
Prime Minister David Cameron has spoken with Kenya's president, who briefed him on "the current situation and explained that Kenyan security forces were bringing the situation under control," according to a statement released by 10 Downing Street.
Cameron "passed on his sincere condolences and assured President Kenyatta that our thoughts were with him and all the people of Kenya at this difficult time," it said.
"The prime minister said we were ready to provide any assistance we could."
Two French citizens are among the victims in the attack, according to a statement released by the Elysee Palace.
President Francois Hollande "condemns in the strongest terms this cowardly attack and shares in grief with the family members of our countrymen," the statement said.
"The president also expresses his complete solidarity with the Kenyan authorities."
Prime Minister Stephen Harper confirmed the deaths of two citizens, including one diplomat, in the attack.
He identified the diplomat, a liaison officer for the Canadian Border Services Agency in Nairobi, as Annemarie Desloges.
"Terror attacks like this seek to undermine the very values and way of life that Canadians cherish, and they reinforce the need for us to continue taking strong actions to protect the safety of Canadians no matter where they are in the world," Harper said.
"Acts of terror cannot be allowed to go unpunished. Canadian staff at our mission are offering Kenyan authorities every possible assistance to bring the perpetrators of this heinous attack to justice."
CNN's Chelsea J. Carter and Neda Farshbaf contributed to this report.