The Democratic Republic of Congo government on Thursday officially declared a ceasefire in the embattled east following a peace deal signed by warring parties, the defence ministry said.
In a statement, the ministry said "the ceasefire is decreed, this day January 24, 2008, as well as the cessation of hostilities" in Nord-Kivu and Sud-Kivu provinces, under an "act of engagement" signed Wednesday by all parties to the conflict.
"Formal orders have been sent to the commanders of both military regions," said the text, signed by Defence Minister Chikez Diemu.
The United States and Europe hailed the "historic opportunity", but United Nations staffers said much work remains to be done.
Meanwhile, Rwandan Hutu rebels based in DR Congo said they were ready to return across the border.
The "act of engagement" was signed by the rebel movement of ex-general Laurent Nkunda, warring militias in the Kivu provinces and the government at the end of a regional peace conference that began on January 6 at Goma, Nord-Kivu's capital.
All parties, including the military, have undertaken to stop fighting immediately, agreeing not to rearm.
"The United States welcomes the signing of a peace agreement with the goal of helping bring lasting stability to eastern Congo and addressing the underlying causes of the conflict," White House spokeswoman Dana Perino said in a statement.
"We call on all parties to ensure urgent implementation of the agreement," she added.
"I am aware of the new challenges... but nonetheless this agreement is a historic opportunity for the Great Lakes region," European Union Development Commissioner Louis Michel said.
Alan Doss, the new chief of the UN mission in DR Congo, MONUC, told AFP "now we must get down to work."
MONUC, which has already posted 90 percent of its 17,000 peacekeeping troops in the ravaged east, plans to deploy them to create buffer zones in trouble spots vacated by the rival sides, Doss added.
Rwandan Hutu rebels said they were ready to return home, a Congolese foreign ministry spokesman said.
Representants of the Democratic Forces for the Liberation of Rwanda (FDFL) and the Rally for Unity and Democracy (RUD) "are ready to return to Rwanda", said Claude Kamanga, spokesman for minister Antipas Mbusa Nyamwisi, after travelling to Mbuakinua, some 160 kilometres (100 miles) north of Goma to meet rebel leaders.
Kamanga said the RUD had "undertaken to sign up to the ongoing peace process" provided the international community "assure (our) security and a return to Rwanda with full dignity".
Rwandan Hutu rebels, estimated to number 6,000 in DR Congo by the UN, are accused by Kigali of actively participating in the Rwandan genocide of 1994, which killed 800,000, mostly Tutsis, according to the UN.
Nyamwisi stressed that the UN-backed joint Congolese-Rwandan deal signed in Nairobi, Kenya, in November 2007, would facilitate their resettlement, either in Rwandan military or civilian life.
"You don't want to reach agreement on peace while keeping the rifle in your hand. Talks between Rwandans, that's for Rwanda to obtain," he told them, according to his spokesman.
The violence in the two provinces has driven more than a million people in the region from their homes, particularly in the north.