Voters in Tana River defied the duck-to-dawn curfew and started queuing at polling stations as early as 5am on Tuesday.
Acting Interior CS Fred Matiang'i enforced the curfew due to sporadic attacks by suspected al Shabaab militants.
There were minor delays as voting materials arrived late due to transport problems.
In Kipini, materials reached late after a lorry was area at the border or Tana and Lamu counties.
Tana River has 118,327 registered voters, three constituencies and 308 polling stations.
County returning officer Mohamed Gonjobe told journalists the exercise ran smoothly in a majority of polling stations.
He said while KIEMS kits had problems, they were able to sort out the problem, leading to minimal disruption.
ODM governor candidate Dado Godana claimed his agents were unable to access polling stations.
"My party agents were denied access to Garsen and Bura constituency stations despite being duly nominated by the party," he told the press.
He is facing off with incumbent governor Hussein Dado, Nuh Nassir (Wiper), Danson Mungatana (KPP) and Jilo Algi.
But the county returning officer said parties should have ensured their agent had the required badges.
CCU's Senate candidate Maur Bwanamaka said he was happy with the process, adding the curfew ensured peaceful elections.
Eldoret town in Uasin Gishu county also had a high voter turnout and high security presence.
GSU teams patrolled and police manned queues.
IEBC officials delivered most voting materials on time, although tens of voters complained their names were missing from the register.
"We didn't have major challenges and voting went on well in most areas," said county returning officers Winston Nyonje.
Read:
Uasin Gishu has 450,050 registered voters and 868 polling stations, the highest in the North Rift.
A tight race is expected between governor candidates Jackson Mandago and Bundotich Buzeki.
"The exercise went on very well and we hope the counting of votes will similarly be smooth so at the end of the day residents are seen to have exercised their democratic rights," Mandago said after voting at Kuinet, near his home.
Buzeki, who voted at Arap Moi Primary in Ainabkoi, also expressed satisfaction with the election.
Other candidates who voted in the region are DP William Ruto, Kapseret MP Oscar Sudi, Senator hopeful Margaret Kamar and woman representative hopeful Gladys Shollei.