Emergency supplies will be sent to refugee camps
The 33 tonnes of water-cleansing equipment and bedding provided by Oxfam arrived in neighbouring Rwanda on Sunday and is being moved by road to refugee camps set up on the border.
An estimated 400,000 people have been displaced by Thursday's eruption near the eastern town of Goma, with many fleeing to Rwanda.
Powerful earth tremors are still being felt on both sides of the Congo-Rwanda border, but experts are divided as to whether there is further risk to the town.
£2m aid package
Meanwhile conditions are worsening at the makeshift refugee camps in Gisenyi.
UN officials are also worried that people displaced by the eruption have been drinking contaminated water from Lake Kivu, which could cause a cholera outbreak.
The Oxfam-chartered aircraft left Manston Airport in Kent on Saturday evening for the Rwandan capital Kigali.
The flight was funded by the UK Government as part of an emergency £2m aid package pledged in response to the eruption.
The Oxfam aid is worth £150,000 and consists mostly of water purification kits to provide clean water for drinking and sanitation for 50,000 people.
The charity says it will send more aid if required, and other agencies are also carrying out relief efforts.
The BBC's Andrew Harding says the international aid efforts will have to follow the refugees returning home.
'Despair'
The Merlin charity is recruiting nurses from the thousands returning to Goma to help treat victims for burns, smoke inhalation and other problems at a border clinic it opened on Sunday.
A second clinic is due to open in Goma on Monday.
Merlin's logistician Christophe Petit said local charity workers had lost everything in the eruption.
"They have aged 10 years in 48 hours. It is just so hard to imagine their despair," he said.
He said one local staff member called Jeannot had taken his children to safety in Rwanda before returning to the city to help in the clinic.
"Jeannot is just one of the many thousands who have seen homes ruined and lives destroyed in little over 72 hours, and yet he is risking himself by coming back here doing what he can to help his fellow Congolese."
Humanitarian specialists
International development minister Hilary Benn told BBC News: "There will need to be more support, because initial reports suggest that large areas of farmland immediately around Goma have been destroyed.
"That's going to create difficulties in the longer term for food supply and people earning a living."
Other countries which have committed help include France, Belgium, Germany and the United States.
Two UK humanitarian specialists are due to arrive in Kigali, where Britain's international development department has an office, on Monday morning.
And a team of relief workers from Christian Aid is also flying to Rwanda with £50,000 in emergency relief aid.
The Catholic Aid Agency, Cafod, is supplying £50,000 in aid through agencies in the region to provide blankets, tents, food and cooking utensils.
Foreign Secretary Jack Straw is due to visit the Central African nation on Monday to urge leaders to end the country's years of civil war.