Djibouti (AFP) - Voters in Djibouti went to the polls on Friday, with iron-fisted ruler Ismail Omar Guelleh expected to extend his 17-year rule in the strategic African nation courted by world powers.

Voting was calm but slow through the morning and early afternoon, after some opposition parties called a boycott, as they have done in previous elections.

Six candidates are vying for the presidency in the tiny Horn of Africa country, whose location at the gateway to the Red Sea has attracted powers such as the United States, France and China as a prime location for military bases.

Guelleh is the clear frontrunner, predicted to win a fourth election victory in the former French colony against a fractured opposition.

Results are expected as early as Friday evening from the election in which 187,000 people -- around a fifth of the population -- are eligible to vote.

Looking relaxed and smiling, the head of state cast his vote in the centre of Djibouti City accompanied by his wife.

"I'm very confident", he said. "I think the vote will go well."

Voter Wihib Rageh, a 46-year-old technician, said he backed Guelleh, shrugging off his already-long tenure.

"Time doesn't count. What counts is what the person does. The main thing is to build the country," he said.

- 'We need change' -

But in the dilapidated district of Balbala, a group of young jobless people disagreed as they watched voters head to a polling station.

"I'm not voting, I'd rather stay at home," said one.

"We need something different," said Hussein, who -- like some 60 percent of Djibouti's population -- is unemployed.

Several opposition candidates complained that their representatives had been turned away from a number of polling stations.

"We demand that the government fix this and organise transparent, free, fair and just elections," independent candidate Jama Abderahaman Djama told AFP.

With a population of 875,000 people, Djibouti is little more than a port with a country attached, but it has leveraged its position on one of the world's busiest shipping routes.

It is home to Washington's only permanent base in Africa, which is used for operations in Yemen -- just across the Gulf of Aden -- as well as the fight against the Islamist Shebab in Somalia and Al-Qaeda in the Arabian Peninsula (AQAP).

- Opposition complaints -

Guelleh, 68, and his Union for the Presidential Majority (UMP) face a divided opposition with his two main opponents, Mohamed Daoud Chehem and Omar Elmi Khaireh, both claiming to represent the Union for National Salvation opposition coalition.

The seven-party opposition alliance was founded in 2013 but has failed to agree on a single candidate, while three of the member parties have boycotted the poll.

Guelleh won the last election in 2011 with 80 percent of the vote, after parliament changed the constitution to clear the way for a third, and now a likely fourth, term.

Following parliamentary elections in 2013 which Guelleh's UMP won with 49 percent of the vote sparking furious opposition claims of fraud, rival parties demanded the creation of an independent electoral commission -- which has never happened.

Opposition groups have complained of curbs on freedom of assembly ahead of the vote while rights groups have denounced political repression and crackdowns on basic freedoms.

This week a BBC team was detained, interrogated and then expelled after interviewing an opposition leader.

Djibouti has launched major infrastructure projects aimed at turning it into a regional hub for trade and services, using money largely borrowed from China, which is planning to build a military base there.

Despite the investment and perky economic growth, four out of five people live in poverty.