South Sudan's Salva Kiir congratulates Kenya's president-elect William Ruto

Kiir said in a statement that Ruto's election demonstrates that a significant number of Kenyans identified with his message of a bottom-up approach to the economy.

 "I write to congratulate you on your election as the fifth President of the Republic of Kenya,"

"Now that the people have spoken, the enormous task ahead of you and your opponents, with whom you campaigned and offered different visions for Kenya, is to unite the people and channel their collective will towards the pressing needs of national development," the statement reads. 

In the same statement, Kiir pledged to collaborate with the Ruto-led government on regional priorities.

South Sudan's President, who has been in office since 2011, joins a growing list of leaders who sent congratulatory messages after Ruto was declared duly elected.

Tanzanian President Samia Suluhu, Zimbabwean President Emmerson Mnangagwa, and New Somalia President Hassan Mohamud were among those who congratulated the newly elected president on Monday.

According to the results, Ruto received 7,176,141 votes, representing 50.49 percent of all votes cast, and achieved the minimum number of 39 counties at 25%.

His main rival Raila Odinga of the Azimio La Umoja One Kenya coalition party got 6,942,930 votes representing 48 percent of the votes cast.