There has been little response to the UN emergency fund, Oxfam says
Yemen could face a serious humanitarian crisis unless immediate steps are taken to stop the fighting, the international aid group Oxfam has warned.
"The emergency in Yemen could ignite into full-blown crisis," it said.
Recent violence between government forces and northern Shia rebels has brought the number of refugees from the conflict to 150,000, UN groups say.
The fighting is reported to be continuing despite a conditional ceasefire called by the government.
Both sides accused the other of continuing attacks.
Oxfam has complained that donations from the international community towards a UN emergency funding appeal has been minimal and echoed UN appeals to both sides to allow humanitarian corridors to be opened.
A recent report by the Carnegie Endowment for International Peace warned that a major humanitarian crisis could result in a large refugee emergency in which the government would not be able to provide rudimentary relief services.
The conflict has been going on since 2004 but fighting has intensified since the Yemeni army launched an operation targeting the rebels in mid-August.
International concern increased after witnesses said more than 80 people were killed in a government air raid on a camp for displaced people a week ago.
The rebels, known as Houthis, complain of discrimination. They say they want greater autonomy and a greater role for their version of Shia Islam.
Both sides see unwelcome influences from abroad, with the government accusing rebels of having Iranian backing and rebels accusing the government of being influenced by Sunni-dominated Saudi Arabia.
The Yemeni government is also battling secessionists in the south and has been criticised by the US for its failure to tackle al-Qaeda militants in the east and pirates off the coast.