FACTBOX: How do Kenya's elections work?

(Reuters) - Kenyans vote on Thursday to elect a new president and parliament.

Here are some facts about Kenya's electoral system:

* Some 14 million Kenyans are eligible to vote.

* Polling stations opened at 6 a.m. (9:00 p.m. EST) and close officially at 5 p.m. (10:00 a.m. EST). The Electoral Commission of Kenya can extend polling hours as it sees fit, after delays in opening were reported in some areas.

* First official results are expected early on Friday.

* Election of the president, for a five-year term, is by direct popular vote. The winning candidate must receive no less than 25 percent in at least five of Kenya's eight provinces plus more votes than his closest challenger nationwide.

* Candidates must also win election to parliament.

* Parliament or National Assembly is the central legislative authority in which there are 210 directly elected representatives, 12 nominated members and two ex-officio members -- the attorney general and the speaker. The maximum term is five years from its first meeting.

* Executive power is vested in the president, vice-president and cabinet. Both the vice-president and the cabinet are appointed by the president.

Sources: Electoral Commission of Kenya; Reuters/Europa Africa South of the Sahara 2008:

(Writing by David Cutler, London Editorial Reference Unit, editing by Mary Gabriel)