Kenyan officials are inking the tiny fingers of babies who accompany their mothers in today's elections, cracking down on queue-jumpers who rent an infant to exploit a rule letting parents with young children skip long lines.

"Every mother who is coming with a kid, we mark the mother and also the kid," said Tabitha Muigai, the presiding officer at a polling station in central Nairobi's Starehe constituency.

The "babies-for-rent" scam was common in past Kenyan elections, often marked by delays and long queues

"(If) a mother comes with a baby we give them a notice that they are not supposed to give other mothers the same kid to come and get favours in the name of jumping the lines," she said.

The "babies-for-rent" scam was common in past Kenyan elections, often marked by delays and long queues. At Muigai's polling station, hundreds of Kenyans queued up around the block, keen to elect a new president, lawmakers and local representatives.

The election is the final time veteran opposition leader Raila Odinga, 72, will face-off against his archrival, incumbent President Uhuru Kenyatta, 55.

Odinga is the son of the country's first vice president and Kenyatta is the son of its first president.

The two dynasties have long been rivals, and Kenyans feel so strongly about the vote that ambulances have been ferrying bed-bound patients to polling stations.

In Kisumu, Odinga's heartland, clerk Stephy Onyango said officials were trained to watch out for the suspicious circulation of babies.

"This one is mine," said mother Joan Awuor, as the fingernail of her sleepy 3-month-old son Ricken was marked when she voted.