Police say more than 40 armed men have been arrested over the latest wave of murders [AFP]

At least four bodies have been found floating on a river near Bujumbura, Burundi's capital, bringing the number of corpses discovered over the past week to 14.

In the latest discovery on Tuesday, the bodies were found in River Rusizi, where it empties on Lake Tanganyika in the north of the country, Julien Nimbona, a local administrator, told AFP news agency on Wednesday

"Since last week, we have found 14 bodies in this area, some of them with their limbs bound and others with machete wounds," he added.

The authorities have insisted that "unidentified armed bandits" were behind the latest surge in violence. Residents in the affected areas, however, say a civil war resuming.

The police said more than 40 armed men have been arrested over the latest wave of murders.

"Twenty-two criminals were arrested and are detained in Mpimba prison [in Bujumbura] while 20 others were arrested in the Democratic Republic of Congo and are being interrogated," Fabien Ndayshimiye, a police chief, said on Thursday.

Election violence

Ndayshimiye refused to elaborate on the identity of those arrested.

A police source, speaking on condition of anonymity, said most of those arrested belong to opposition parties, including the Movement for Solidarity and Democracy (MSD) and the former rebel National Liberation Forces (FNL).

He accused these groups of creating instability following the latest local elections.

Since a string of local elections kicked off in May, tensions have grown in the small central African country with opposition parties withdrawing from the polls alleging fraud by the ruling party.

Agathon Rwasa, the main political rival of Pierre Nkurunziza, Burundi's president, has abandoned his government duties and gone back to the bush, fuelling speculation that FNL group has taken up arms, only a year after laying them down.

The three-month-long electoral marathon had been seen as an opportunity for Burundi to prove its democratic credentials and seal the end of a civil war that has killed at least 300,000 people dead since 1993.