The deadline set by the Democratic Republic of Congo for foreign militias to leave the country has expired.
Militia have been most active in the east of DR Congo
The government in Kinshasa has pledged action against them and against any new invasion by outside forces.
President Joseph Kabila issued the ultimatum three weeks ago. Officials say there is no sign of compliance by the mostly Rwandan and Ugandan militia.
A peace deal ended DR Congo's civil war in 2002, but the government exerts little control in the east.
Uganda has meanwhile threatened to use force against Lord's Resistance Army rebels sheltering in DR Congo.
A Congolese government spokesman, Henri Mova Sakanyi, said the threat was not serious, but reaffirmed that if the thousands of foreign militiamen did not disarm voluntarily the army would act.
Analysts, however, say the Congolese army is in pretty poor shape and may not be capable of disarming the militias. Some soldiers have recently defected in the east to rejoin former rebel groups.
Even the 17,000 United Nations peacekeepers in DR Congo are not enough, said Ibrahim Gambari, UN under secretary general for political affairs.
UN patrols are a reminder that life is still far from normal in eastern DR Congo
"To disarm them all will require an enormous peacekeeping force, which the UN doesn't have, and which member states are not willing to fund," he said.
Earlier on Thursday, Ugandan President Yoweri Museveni warned that his army would again enter DR Congo unless Ugandan rebels from the Lord's Resistance Army who recently crossed the border were disarmed.
"If the international community does not come in to do it, we shall go there," he told a news conference in the Ugandan capital, Kampala.
The BBC's Will Ross in Uganda says many Congolese as well as international observers will find the Ugandan president's words rather worrying.
But Mr Mova said he did not think President Museveni was serious, and pledged to repel any attack.
"He will not attack, these are only threats," he said.
"If Uganda, Rwanda, or any other country launches an attack on the DRC, we will fight."
Congolese Defence Minister Adolphe Onusumba this week told the BBC that the LRA rebels would be disarmed and sent back to Uganda.
Rwandan Hutu militias are also active in eastern DR Congo, and Rwanda has frequently threatened to invade to disarm them.
They are accused of responsibility for the 1994 genocide, in which some 800,000 Tutsis and moderate Hutus were killed.
Uganda and Rwanda sparked DR Congo's civil war by invading and supporting local militias, after accusing DR Congo of backing rebel groups.
Under the 2002 peace deal, all militias were supposed to be disarmed.