"One hundred fifty trucks can't cover our vast national territory which doesn't even have the road infrastructure," said Augustin Kabuya, spokesman of the main opposition Union for Democracy and Social Progress (UDPS).

The conflict-ridden DR Congo sprawls over 2.3 million square kilometres (890,000 square miles), making it the largest country in sub-Saharan Africa, some two-thirds the size of Western Europe.

The former Belgian colony boasts just 27,877 kilometres (17,322 miles) of roads, President Joseph Kabila said in July. By comparison, France alone has more than a million kilometres.

Kabuya said the handover of the trucks, planes and helicopters, conducted with great fanfare on Monday, was "staged" to lend international credibility to the elections.

"We know (however) that... Corneille Nangaa is not ready to organise the elections on December 23," Kabuya told AFP, referring to the head of the Independent National Electoral Commission (CENI).

During Monday's ceremony, the Congolese authorities said the vote -- postponed in 2016 and again last year -- would go ahead without help from the international community.

Previous elections, in 2006 and 2011, took place with material and logistical support from the UN mission to the DR Congo known as MONUSCO.

However relations between MONUSCO, the world's largest peacekeeping operation, and Kabila's government have long been strained.

Kinshasa has repeatedly demanded the winding down of the mission, whose military observers were deployed in 2000 during the Second Congo War. The force now counts more than 15,000 troops, 1,000 police and 2,500 civilians in its ranks.

Conflict persists notably in the North Kivu province on the country's eastern border, which has been subject to consecutive waves of bloodshed and brutality involving militias, rebel groups and government forces for more than 20 years.

- Kabila protege in the running -

Speaking at the UN General Assembly in September, Kabila vowed to "oppose any interference in the electoral process under way" and said that his country would cover the full cost of the December polls.

Asked to comment on Tuesday, MONUSCO spokeswoman Florence Marchal said the mission would provide logistical support if asked.

"But so far there has been no request," Marchal told AFP.

The presidential, legislative and municipal elections, set for December 23, will notably yield a successor to Kabila, who is barred by term limits from seeking re-election.

Kabila, 47, has been in power since 2001. His second and final elected term in office ended nearly two years ago, but he stayed in office thanks to a caretaker clause in the constitution.

Months of feverish speculation over his intentions, marked by protests that were bloodily repressed at a cost of dozens of lives, ended in August when he threw his weight behind Emmanuel Ramazani Shadary, a hardline former interior minister.

UDPS leader Felix Tshisekedi is also among the 21 presidential candidates.