Cyclone Fani has brought "heavy devastation" to parts of India after making landfall on Friday, Christian Aid has warned.
The cyclone has caused the worst damage in Odisha, the poorest state in India, where many have been left without power.
Around a million people were evacuated ahead of the cyclone, the strongest storm to hit India in five years.
Christian Aid said that it was also getting ready to respond in Bangladesh, where the storm was expected to arrive on Friday night.
The aid agency said there was already need in the country as thousands of people who took shelter ahead of the storm are lacking clean water, food and sanitation.
Madara Hettiarachchi, head of Humanitarian Programmes for Christian Aid, said its local partners were airlifting provisions to those in affected areas.
"The cyclone is causing heavy devastation; trees have been uprooted, airports are shut and electricity has been cut off," she said.
"Our local partners are responding quickly in India, prioritising the most vulnerable. They will airlift shelter items and provide food and water filters to those in relief camps and cyclone shelters."
Hettiarachchi said it was necessary to act now before the storm worsens.
"Winds of up to 100km/h are now being felt in the coastal areas of Bangladesh where one million people are likely to be affected," she continued.
"Up to 30,000 have taken shelter but there isn't enough food, water or sanitation provisions to meet the scale of need. We are expecting the cyclone to reach Bangladesh tonight and we are ready to respond.
"We shouldn't wait for the situation to get worse, or for more people to die. We need to act now."
