Having emerged from an election fraught with strife and irregularities, Burundi's President Pierre Nkurunziza has been sworn in for a controversial third term in office.

The impromptu ceremony caught many Burundians unaware as Mr Nkurunziza had been expected to be sworn in next week.

At least 100 people have died in protests since Mr Nkurunziza announced in April he would run for a third term.

The government accuses the opposition, which says the third term is illegal, of causing the violence.

In his inauguration speech, Mr Nkurunziza promised to end the violence within two months.

No foreign head of state attended the inauguration.

Burundi's government says a number of countries apologised for not sending their delegates, because of the change of date.

 Nkurunziza’s decision of being sworn sworn in a week ahead of schedule, has outthought the opposition, headed off predicted protests and gave any heads of state who didn't want to come, a good excuse for not turning up.

The African Union, European Union and the US State Department have all expressed concerns that July's election was not free and fair.

The UN observer mission said the election was not free and credible and was held "in an environment of profound mistrust" between political rivals.

The African Union did not send observers - the first time it has taken such a stance against a member state.