Foreign Secretary David Miliband was flying to the Democratic Republic of Congo today as fierce fighting rages between the African nation's government and rebel forces, the Foreign Office confirmed.
Mr Miliband will also visit Rwanda as diplomatic efforts get under way to try and bring an end to the crisis.
Envoys from the US and UN have been sent in to help set up negotiations as aid agencies warned of a humanitarian catastrophe.
Yesterday, a ceasefire appeared to be holding in the violence-hit eastern city of Goma.
On Wednesday tens of thousands of residents, refugees and government soldiers fled the city as rebels advanced.
Congolese soldiers were reported to have killed at least nine people and looted homes and stores in the eastern provincial capital.
Rebel leader Laurent Nkunda has called for the urgent disarmament of a Rwandan Hutu militia that he says works with the government.
He said his fighters had retreated seven miles from Goma.
But he has threatened to take the city unless UN peacekeepers guarantee the ceasefire.
Despite agreeing to a UN-brokered ceasefire in January, Nkunda resumed fighting in August.
More than 200,000 people have been forced from their homes over the past months.
Aid agencies are now turning their attention to providing the displaced with food, shelter and support.
Juliette Prodhan, head of Oxfam in Congo, yesterday said international staff had been evacuated from Goma as a "precautionary measure".
She said: "We will continue to monitor the situation closely, in the hope of being able to resume humanitarian assistance to those who so badly need it in the area.
"If we cannot get back into the camps after two weeks, the situation will become more complicated.
"Further violence will only cause more human misery and suffering for people who have already suffered too much."
Save the Children began the evacuation of its staff in the province of North Kivu because of the fighting.
Hussein Mursal, its director in the country, said: "The conflict is now threatening the lives of our aid workers so we have temporarily withdrawn our staff to safety.
"With the humanitarian crisis worsening day by day, it's vital for us to be able to get help to communities, but the security situation is making it impossible."
ActionAid called for a guaranteed safe passage for humanitarian workers and assistance to those in need of help.
The agency Merlin also moved some of its team to safety in a nearby town in Rwanda.
The African Union is to hold crisis talks today.
EU efforts have also been ongoing to bring Rwandan president Paul Kagame and Congolese president Joseph Kabila together.
The UN said its first priority was to sustain the ceasefire. It was considering redeploying troops from other parts of the country.
Foreign Office Minister, Lord Malloch-Brown, has called for "heavy diplomatic pressure in both Kinshasa and Kigali" to resolve the situation.
Meanwhile, there was growing concern for 39 wildlife rangers who fled into dense forest after their headquarters were stormed by rebels on Sunday.
The rangers, who patrol and protect Virunga National Park assisted by EU funds from the Zoological Society of London (ZSL), have no food, water or shelter and are surrounded by warring armed groups.
More than 120 rangers have died in the last decade of civil war and instability while protecting Virunga's wildlife.
Britain is to provide £5 million in additional aid to the Democratic Republic of Congo to help those affected by the crisis, it was announced today.
The money will be on top of the £42 million the UK provides to the country in financial support every year as one of its biggest donors.
International Development Secretary Douglas Alexander said he was "deeply concerned" about the situation in North Kivu.
"Whilst we urge both sides to make the ceasefire permanent and ensure law and order is restored, we must remember the ordinary civilians who are once again suffering the most," he said.
"That is why I am today announcing that the Department for International Development will provide a further £5 million in aid to ensure people have food, water and shelter.
"We have a team in the country who are monitoring the situation and helping to coordinate the humanitarian response.
"All sides need to respect the rights of civilians and support the access, property and staff of humanitarian agencies who are seeking to help those in desperate need."
Shadow international development secretary Andrew Mitchell, who has visited both Congo and Rwanda in the past year, called for the United Nations peacekeeping force to be bolstered with reinforcements.
At present, they are outgunned in Goma by the 8,000-strong FDLR group, made up of the remnants of the regime responsible for the 1994 genocide in Rwanda, he said.
"Unless the UN is reinforced, it is simply not going to be able to tackle this problem," Mr Mitchell told BBC Radio 4's World at One.
Mr Mitchell said that, despite agreements from the Congolese and Rwandan governments and 22 armed groups in the region to lay down their arms, the UN had not yet delivered on a Security Council resolution passed in March to deal with the situation in Goma.
"It is a matter of ensuring that the will of the international community and the participants, as expressed through these different agreements, is enforced on the ground," he said.
"You can't do that unless we reinforce the UN at this point to take on these problems."
Liberal Democrat foreign affairs spokesman Edward Davey said: "It is critically important that the UN, the Foreign Secretary and his EU counterparts work together with urgency on this crisis.
"The UN mission in DR Congo has been starved of resources for far too long, making a difficult job impossible.
"Britain, with our allies, should either contribute resources or help African countries who have the troops but not the cash."
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