NAIROBI, Kenya (CNN) -- Throngs of Kenyans lined up Monday to choose their next president in a tight, anxiously awaited general election marred by isolated violence.
Residents were eager to avoid a repeat of the disastrous 2007 election, which plunged the nation into ethnic violence after results were disputed.
"We are excited; this has been a long time coming," said Mark Kamau, who lives in the capital of Nairobi. "We are ready to show the world that this is not the Kenya they saw in 2007."
Hours before the polls opened, a group of heavily armed men attacked a police post in the port city of Mombasa, killing at least 10 people, including two police officers, officials said.
David Kimaiyo, inspector general of Kenyan police, said a group of men approached police officers manning a post between 9 and 10 p.m. and disobeyed orders to stop. Police fired on the men, who fled into a nearby slum, he said.
When police called for backup, about 200 men ambushed them on a road, Kimaiyo said.
Prime Minister Raila Odinga blamed the attack on the Mombasa Republican Council, a separatist group that wants Mombasa, the second-largest city in Kenya, and its surrounding coastal area to secede.
Kimaiyo said police had confirmed the group's involvement in the attack.
Elsewhere, ETV correspondent Soni Methu told CNN that her crew came across the bodies of five people at a polling station in the coastal town of Kilifi. Two of the bodies were wearing police uniforms; one had a Kenya Wildlife Service uniform on, Methu told CNN.
Also, in Mandera -- near the border with Somalia and Ethiopia -- witnesses said bombs exploded at two polling stations. Red Cross Mandera Coordinator Abdi Ahmed said three people were slightly injured.
And in the Kenyan town of Kitengela, south of Nairobi, at least 20 people were hospitalized after a stampede at a polling station, CNN affiliate NTV reported.
Voting in the rest of the country has been largely peaceful.
The stakes are high for the election, the first since the disastrous 2007 vote.
After that election, the government boosted security and set up an ambitious new constitution, making it one of the nation's most complicated polls since it gained independence from Britain in 1963.
Eight contenders are vying for the presidency, including frontrunners Odinga, the prime minister, and his deputy, Uhuru Kenyatta.
Recent polls show the two in a tight race, prompting analysts to raise the possibility of a second round of voting next month.
Kenya's constitution calls for a runoff within a month of the results if no candidate gets more than 50% of the vote.
After the last election, the nation also revamped various political systems, including the constitution, the electoral process and the judicial system. It said the new system will empower citizens and local governments, ensuring a peaceful election.
"It is one thing to change the constitution, but we have to change our underlying issues of ethnic sentiments that have dated years," said Kamau, the Nairobi resident.
During the last election, Odinga disputed results mandating the incumbent President Mwai Kibaki as the winner, alleging the outcome was rigged.
Supporters loyal to both leaders took to the streets in protest, pitting ethnic groups loyal to both against one another.
More than 1,200 people were killed and hundreds of thousands displaced -- the worst violence since the nation gained independence.
Optimistic, but prepared
Leading up to this election, Kenyans have pledged peace, with candidates declaring they will settle any election disputes in court.
Candidates have implored their supporters to avoid bloodshed, no matter the vote's outcome.
But despite a wave of optimism, some citizens remain wary.
"I don't know what possessed people last time," Kamau said of the violence. "I hope there will be no violence. I'm waiting for Kenya to restore my faith this time."
But as he waits, he is prepared. His refrigerator is stocked and his car is filled with fuel.
"Just in case," he said. "You never know."
'My main issue'
The economy, security and the fight against corruption, which is rampant in the country, are among voters' top concerns in the election.
The election also has a unique challenge. Kenyatta has been indicted by the International Criminal Court for allegedly inciting a local militia to conduct reprisal attacks in the last election. He has denied the charges.
His running mate, William Ruto, also faces ICC charges.
Despite the indictment, Kenyatta enjoys massive popularity. But some voters are afraid the international community will isolate the nation if a candidate facing ICC charges is elected.
Dominic Muia, 35, was in line at 5 a.m. to cast his ballot in the town of Nakuru.
"My main issue is the economy," he said. "I'm voting for Uhuru because he is younger and has a better vision to move the country forward."
At 51, Kenyatta would be the youngest Kenyan president ever if he wins. Odinga is 68.
'Things an average citizen worries about'
Harrison Mario, 37, said his vote is based on issues and policies, and will go to Odinga.
"Basically, he has been fighting inequality." he said. "He has been campaigning for the less fortunate -- his manifesto focuses on security, education and food -- things an average citizen worries about."
Both leaders are campaigning on almost the same policies, leaving the more than 14 million registered voters to choose based on criteria including personality, ethnicity and links to political parties.
"I don't know that much about their differences, so I'm voting for the candidate of my favorite political party," said Susan Kamau, who lives in Nairobi. "In short, I'm voting on loyalty to my party, not issues."
In addition to the presidential race, the nation will also pick governors, senators and a slew of other local candidates under the new constitution.
Whoever wins, the race brings back memories of a political dynasty.
Kenyatta's father was the nation's founding president, while Odinga's father was his vice president in the 1960s.
Both started out as allies in the fight against independence from Britain, but they had a falling out that led Jomo Kenyatta, a Kikuyu, to force out Jaramogi Odinga, a Luo, as his vice president.
Their tense history has strained relations for decades between Kikuyus and Luos.
-- Nima Elbagir reported from Nairobi, and Faith Karimi reported and wrote from Atlanta.
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