A UK charity appeal to help hundreds of thousands of people fleeing violence in Myanmar has been launched by the Disasters Emergency Committee (DEC).
The government said it would match the first £3m donated by the public.
More than 500,000 Rohingya Muslims have left the country, formerly known as Burma, with many now staying in makeshift camps in Bangladesh.
DEC chief executive Saleh Saeed said the exodus was a "catastrophe" and left many in need of shelter and medicine.
International Development Secretary Priti Patel said she was "appalled" by the violence in Myanmar and insisted the government would do "everything it possibly can" to help.
"It is utterly intolerable that the military who are responsible for this inhumane catastrophe have not heeded calls for restraint," she said.
Most of those displaced are Rohingya people, who have fled across the border to Bangladesh after a military offensive in Myanmar's Rakhine state.
The violence erupted on 25 August after Rohingya insurgents killed 12 members of the security forces, prompting a military crackdown.
'Exhausted and traumatised'
DEC's member charities are already in Bangladesh delivering emergency aid - but they said they needed more funding to reach people in need.
Mr Saeed said people were arriving "exhausted and traumatised" at overcrowded camps across Myanmar's border with Bangladesh.
"Families are living in makeshift shelters or by the side of the road with no clean drinking water, toilets or washing facilities," he said.
"This humanitarian catastrophe is unfolding in a country that is already reeling from the worst floods in decades."
DEC, which represents 13 UK charities, will broadcast its campaign video on major UK television stations.
The UN said more than 410,000 Rohingya have fled to Bangladesh, saying many had arrived with injuries sustained during the crackdown.
Aung San Suu Kyi, Myanmar's de factor leader, has been widely criticised for her response to the Rohingya crisis.
