Kenya has been hit by bombings and shootings blamed on Somali extremists that have sharpened political tensions as the country braces for ethnic violence in upcoming presidential elections in which two candidates have been charged with crimes against humanity.

The East African state was already on edge amid fears it will be plunged into an orgy of political bloodletting as happened after a disputed presidential poll in December 2007.

"Election-related violence has already started," declared Gabrielle Lynch of Britain's Warwick University, which monitors Kenya's tribal conflict zones.

Kenyan Prime Minister Raila Odinga, who ran in the fateful 2007 race, is running again in the March 4, election.

The opposing team is Uhuru Kenyatta, the son of Kenya's founding president and one of the country's richest men, and his running mate William Ruto, a former Cabinet minister dismissed on suspicion of corruption.

They're leading most opinion polls, even though they're among four Kenyans charged by the International Criminal Court in connection with organizing violence in the bloodletting of early 2008 that followed the last presidential election.

The attacks in Kenya in recent days were seen as retaliation for the country's participation in a yearlong regional military offensive against al-Shabaab militants in neighboring Somalia that drove the Islamists out of their urban strongholds and into the bush.

Kenya hosts more than 500,000 Somali refugees. Most of the attacks that began Sunday occurred in the Eastleigh district of Nairobi where there's a large Somali community with links to al-Shabaab, which is connected to al-Qaida.

Street battles flared in the quarter, known as "Little Mogadishu" after the war-battered Somali capital, in November between Kenyans and ethnic Somalis after a bomb on a minibus killed seven people.

But the spillover of the Somali bloodletting, that's raged for more than two decades in the absence of a functioning government, is probably the least of Kenya's troubles.

Kenyans are consumed by fears they'll be ravaged by another wave of ethnic violence linked to the presidential polling.

In early 2008, as many as 1,200 people were killed and the country, once considered the most stable in the region, and up to 250,000 displaced as Kenya was pushed to the brink of civil war.

Rival tribes like the Kikuyu, the Luo and Kalenjin, which backed different candidates, went on the rampage after incumbent President Mwai Kibaki, a Kikuyu, was declared the winner.

Supporters of his rival, Odinga, largely supported by the Luo and Kalenjin, alleged the voting was rigged. That was widely confirmed by international observers, who said both camps were involved in it.

The bloodletting raged for two months, particularly in the volatile Rift Valley. Under mediation by former U.N. Secretary-General Kofi Annan, Kibaki and Odinga signed a power-sharing pact Feb. 28, 2008, under which Odinga became prime minister.

To this day, it remains unclear who was responsible for the ethnic violence and massive displacement that occurred after the 2007 election.

But Kenyan authorities and Fatou Bensouda, chief prosecutor at the ICC in The Hague, agree that some of the violence was highly organized. That conclusion resulted in the charges against Kenyatta, his 2013 running mate Ruto, and two other Kenyans.

The court alleges the candidates hired criminal gangs who carried out some of the murderous rampages.

If the current opinion polls prove to be accurate come March, when Kibaki must stand down after two terms, Kenyatta and Ruto could be elected president and vice president.

That's an outcome many fear could trigger a new spasm of violence.

It may already have begun.

In August, more than 100 people, including women and children, were slain in ethnic clashes in the Tana River district in eastern Kenya.

Three bombings in Nairobi killed at least 10 people within four weeks, although these may have been linked to the Somali crisis.

In another eruption, heavily armed cattle rustlers -- whose activities are often tribal-related -- attacked police in November, killing dozens of officers.

"The stakes as the country prepares to go to the polls in March could not be higher for both the country and the region," observed John Githongo, a former permanent secretary of governance and ethics.

"Kenya's $34 billion economy is the largest in East Africa, constituting more than half that of the region and 60 percent of its middle class."