International Criminal Court prosecutor Luis Moreno-Ocampo on Tuesday warned the main rivals in DR Congo's tense election that he would not tolerate any violence.

"We are closely watching the situation on the ground, and recourse to violence will not be accepted," he said in a statement.

Tension between President Joseph Kabila's camp and opposition supporters has already flared on several occasions before and since the November 28 election.

Human Rights Watch has said at least 18 civilians have already died in election-related violence from November 26 to 28, most of them shot dead by Kabila's presidential guard in Kinshasa.

"We continue to receive multiple reports of violent attacks against civilians, of fighting between rival factions, as well as attacks by armed groups and the national security forces," Moreno-Ocampo said.

"I am also aware of reports of violence by armed groups apparently associated with different political parties, politicians and party officials against demonstrators from opposing parties," he said.

Kabila's main rival Etienne Tshisekedi has issued thinly veiled threats of violence should the current trend giving the incumbent the lead in early tallying not be reversed when full results are released.

Thousands of soldiers were deployed in Kinshasa and other cities in Africa's second largest country amid fears that the conflict-prone country could descend into chaos no matter who is declared the winner.

The Congolese election body said full results would be released Tuesday if logistical hurdles slowing down the counting process were overcome.

"As we have shown in both Kenya and Cote dIvoire, planning and executing attacks on civilians for electoral gain will not be tolerated," the ICC prosecutor said.

The DR Congo has one of the continent's most violent histories, and four cases relating to crimes committed there have already been brought before the ICC.