US President Barack Obama has congratulated Kenya on its successful constitutional referendum vote as a "significant step forward."

"The United States congratulates the Kenyan people and government on the holding of a peaceful, transparent, and credible constitutional referendum," Obama said in a statement.

"This was a significant step forward for Kenya's democracy, and the peaceful nature of the election was a testament to the character of the Kenyan people." he added

The president said the new constitution's approval, by 67 percent, showed the desire of Kenyans to "put their country on a path toward improved governance, greater stability, and increased prosperity."

He pledged the United States would work with the international community "to support the implementation process, and to stand with the Kenyan people as they reach for a better future."

Secretary of State Hillary Clinton earlier Thursday praised Kenyans for turning out in large numbers to hold a peaceful vote, setting aside fears of a repeat of the chaos that marred the nation's last elections.

"Constitutional reform is the centerpiece of the reform agenda that Kenya has adopted for itself. It is aimed at addressing the underlying causes of violence," she told reporters as she stood next to Nigeria's visiting Foreign Minister Henry Odein Ajumogobia.

"I commend the people of Kenya for participating in large numbers and for exercising their right to vote in a peaceful manner," she said.