Chad president wins sixth term

Chad's veteran leader Idriss Deby has won a sixth term as president, provisional election results show, as the army says it's beaten back a column of insurgents advancing on the capital N'Djamena.

Deby, 68, took 79.3 per cent of the vote from the April 11 election after top opposition leaders boycotted to protest his efforts to extend his 30 years in power.

Deby seized power in an armed rebellion in 1990. He is one of Africa's longest-serving leaders and a close ally of Western powers battling Islamist militants in West and Central Africa.

But he has faced repeated insurgencies in the desert north and is also dealing with mounting public discontent over his management of oil wealth and crackdowns on opponents.

The rebel group Front for Change and Concord in Chad, which is based across the northern frontier with Libya, made inroads south after attacking a border post on election day and calling for an end to Deby's presidency.

But it appeared to suffer a sharp setback at the weekend. Chad's military spokesman Azem Bermendao Agouna told Reuters army troops had killed more than 300 insurgents and captured 150 on Saturday in Kanem province, about 300 kilometres from N'Djamena.

Five government soldiers were killed and 36 were injured, he said.

The rebels' leader, Mahamat Mahadi Ali, told Radio France Internationale on Monday that his forces had made "a strategic retreat".

The unrest has raised alarm bells among Western countries which have seen Deby as an ally in the fight against Islamist extremist groups.

The United States ordered all of its non-essential embassy staff to leave the country on Saturday. The British government had urged its citizens to leave the previous day.