Guinea-Bissau has approved a new constitution in a referendum, provisional results showed on Tuesday, expanding presidential powers and reshaping electoral rules ahead of a presidential election scheduled for December.

The West African country led by the military voted on Sunday on reforms allowing the president to appoint and dismiss the prime minister and cabinet, create or abolish ministries and dissolve parliament in the event of a grave political crisis.

Under the current constitution, Guinea-Bissau's legislature names a prime minister who appoints a cabinet.

The result gives the military government backing to reshape Guinea-Bissau's political system before the presidential election, but the main opposition party boycotted the vote.

The new constitution was approved by 70% of voters in favour and 30% opposed, according to the provisional results announced by the National Electoral Commission. It also said some 544,060 people had voted, almost 60% of registered voters.

The constitution will cut the size of parliament to 65 seats from 102 and reduce the number of electoral constituencies to 12 from 29.

It further requires presidential candidates to have lived continuously in Guinea-Bissau for the preceding five years.