Hundreds of Congolese rebels withdrew Friday from frontline positions around Goma as promised under a regionally brokered deal, as police entered the key eastern city to take over control.
The UN Security Council meanwhile imposed sanctions against two rebel leaders accused of killing children and others who tried to flee their force.
The council said it had ordered a global travel ban and assets freeze against Baudoin Ngaruye and Innocent Kaina, both top military leaders of the M23 movement which has grabbed territory in eastern DR Congo.
The M23 rebels, army mutineers who seized Goma last week in a lightning advance, have said they will withdraw 20 kilometres (12 miles) from the city, the main town in the Democratic Republic of Congo's mineral-rich east.
But even as rebel forces started to pull back, M23 military leader Sultani Makenga accused United Nations peacekeepers -- to whom the gunmen have agreed to hand over the territory -- of "beginning to block" the movement of rebel equipment out of Goma.
"We are waiting for the problem to be solved to withdraw," Makenga told AFP from Sake, some 30 kilometres (18 miles) west of Goma, where an AFP reporter saw rebels trekking down from steep hillside positions carrying packs and crates of ammunition.
He said that if the problem wasn't fixed, the pullout from Goma could be delayed.
UN spokesman Madnodje Mounoubai said MONUSCO had barred M23 from entering the airport because control of the facility had not yet been assigned to a three-way force made up of UN, M23 and regular army forces as agreed under terms of the deal.
International observers monitoring the withdrawal said MONUSCO blocked the airport because M23 were trying to carry out munitions seized from the Congolese army.
Rebels are reported to have seized heavy weaponry and ammunition abandoned by the army, which fled in disarray when the fighters seized Goma and surrounding settlements in the chronically volatile region.
Residents have reported seeing dozens of rebel trucks carrying food and ammunition through the lush green hills on the shores of Lake Kivu toward Goma, pulling back past the wreckage of last week's fighting.
The pullout came as more than 270 Congolese policemen arrived in Goma's port, having crossed Lake Kivu from government-controlled Bukavu some 100 kilometres south, with the army vowing to enter the city the next day.
The policemen were due "to secure the city of Goma after the pullout of M23 rebels", said UN spokesman Mounoubai.
While the rebels still control Goma, Congo's army chief General Francois Olenga has said government troops will enter the city on Saturday.
"We will deploy our units tomorrow," Olenga told AFP. "A battalion will be posted in the city and a company will be posted at the airport."
The rebels' campaign has raised fears of a humanitarian catastrophe and wider conflict erupting from Congo's east, the cradle of back-to-back wars that shook the country and embroiled other nations in the region from 1996 to 2003.
Under a pullout deal struck this week in Uganda with army chiefs from the 11-nation International Conference on the Great Lakes Region (ICGLR), senior officers from the regional bloc are travelling to Goma to monitor the withdrawal.
Rebels, understood to be made up of some 1,500 fighters, will leave a company of 100 men at the airport alongside government troops, and neighbouring Tanzania is also expected to send a company of soldiers to the airport under the regional deal.
-- Fears Of Looting --
Decades of conflict between multiple militia forces -- as well as meddling by regional armies -- have ravaged Congo's east, which holds vast mineral wealth including copper, diamonds, gold and key mobile phone component coltan.
UN experts have accused Rwanda and Uganda -- which played active roles in DR Congo's 1996-2003 wars -- of supporting M23, a charge both countries deny.
The Security Council and the United States have already ordered sanctions against Makenga.
Ngaruye, a deputy to Makenga, "is responsible for executions and torture of deserters within the M23," said a sanctions committee statement.
Innocent Kaina "oversaw the recruitment and training of over 150 children for the M23 rebellion, shooting the boys who had tried to escape," the statement added.
Britain on Friday froze $33.7 million (25.9 million euros) in aid to Rwanda following "credible and compelling reports of Rwandan involvement with M23," International Development Secretary Justine Greening said, a move condemned by Kigali.
Civilians in Congo, many of whom have had to flee repeated rounds of fighting over several years, are suffering.
Aid agencies are struggling to cope with the newly displaced, with some 285,000 people having fled their homes since the rebels began their uprising in April.
The instability in DR Congo's east was exacerbated by the aftermath of the 1994 genocide in Rwanda, when Hutus implicated in the killing of some 800,000 mostly Tutsi victims fled across the Congolese border after Tutsi leader Paul Kagame came to power.
M23 was founded by former fighters in a Tutsi rebel group whose members were integrated into the regular army under a 2009 peace deal they claim was never fully implemented.