"I will not let such attacks go unpunished," said Luis Moreno-Ocampo of the attack in the Sudanese region in September last year in which 12 African Union peacekeepers were killed and eight wounded. He did not name his targets however.

Human rights watchdogs welcomed the move and senior Darfur rebels vowed to cooperate with the court, while denying involvement in the attack.

The announcement today came four months after Mr Moreno-Ocampo asked the court for a warrant for Sudan`s President Omar al-Beshir for genocide, war crimes and crimes against humanity in Darfur, where the UN says 300,000 people have died in conflict since 2003.

Presenting evidence to a panel of ICC judges in The Hague, the prosecutor said he intended pursuing the rebel leaders for war crimes.

"There are reasonable grounds to believe that these rebel commanders bear criminal responsibility ... for murder, intentionally directing attacks against personnel and objects involved in a peacekeeping mission and pillaging."

He blames them for an attack on African Union (AMIS) peacekeepers in Haskanita, Darfur.

"As commanders, they planned and directed the attack," said the prosecutor. "They commanded forces of around 1000 men in a convoy of approximately 30 vehicles mounted with heavy weapons to attack AMIS peacekeepers."

Amnesty International spokesman Christopher Hall said: "This announcement is a clear demonstration that the ICC is investigating individual members of all groups that are party to the conflict."

Human Rights Watch director Richard Dicker said the move was crucial for "protecting those who protect civilians".

"Any hope for restoring security for civilians in Darfur depends on peacekeepers being able to do their job," he said.

Darfur`s Justice and Equality Movement (JEM) rebel formation said it would cooperate with the ICC, while denying responsibility for the attack.

"We support its procedures against al-Behir, so JEM is in favour of the ICC," a London-based leader, Tahir el-Faki, said.

Three other rebel commanders also denied being on the prosecutor`s list.

"We are ready to go to any place if he wants us," said Abu Bakr Kadu, a commander of the Sudan Liberation Army-Unity (SLA-Unity) movement.

Ahmed Abdel Shafie, who heads another SLA faction, said: "We condemned any action against the peacekeeping force and the innocents, no matter from which side the perpetrators."

The prosecutor would not divulge the names of the rebel leaders or of their militia groups, as this might hamper the investigation.

This is Mr Moreno-Ocampo`s third Darfur case, but his first against rebel groups.

He had presented "very strong evidence", but had no indication of when a decision might be taken, he said.

"It is now in the hands of the judges."

In May 2007, the ICC issued warrants against Sudan`s former interior minister Ahmad Harun and Ali Kushayb, a leader of the government-backed Janjaweed militia, for war crimes and crimes against humanity in Darfur.

A panel of judges is reviewing Mr Moreno-Ocampo`s request in July for a warrant for al-Beshir, who has shrugged off the threat and refuses to hand over Harun and Kushayb.

The president declared a ceasefire in Darfur earlier this month.

According to the United Nations, 300,000 people have died and more than 2.2 million have fled their homes since rebels in Darfur rose up against the Khartoum government in February 2003. Sudan puts the death toll at 10,000.

The ICC is the world`s first independent, permanent war crimes court.