Tearfund and Gospel for Asia are calling for prayer as India's east coast braces itself for a cyclone that may be as big as Hurricane Katrina.

The category 5 cyclone has forced the evacuation of 400,000 people as it makes its way across the Bay of Bengal. It is expected to make landfall some time Saturday afternoon local time.

Sudarshan Sathianathan, Tearfund's Head of Region for Asia said. "I fear it could be as bad as the major cyclone that hit the same low-level coastal states in 1999, but I'm hopeful that the destruction and loss of life will not be on the same scale."

The 1999 Orissa Cyclone reached speeds of 190mph and killed 15,000 people. However, Tearfund said much work had been done since then to build safe shelters, prepare communities in their response, and implement evacuation procedures.

"Tearfund's partner teams in Odisha and Andhra Pradesh have response plans, as we closely monitor events," said Sudarshan.

"We can all only hope and pray that the cyclone reduces in scale and speed, and that its course may miss the most vulnerable villages."

The storm follows a period of significant flooding across Andhra Pradesh and Odisha, and comes as thousands of agricultural workers were preparing to harvest the area's vast rice crops. There is concern that the massive tidal surge could devastate what are India's main rice growing areas.

"We ask churches and Christians around the world to pray for the people of east India this weekend," said Sudarshan.

"Reducing the risk of natural disasters, such as cyclones, in this region will have a life-saving impact. If people heed the warnings, and know exactly what to do for themselves, their families and vulnerable neighbours, then there will be something positive to report. Today we watch and wait because humanly we can't avoid a storm this big."

Gospel for Asia's compassionate ministry teams are assembling for relief efforts and praying that God will intervene to lessen the storm's expected effect.

"We have no way to grasp fully all this will mean for the people in these areas and how long it will take to get aid to those in the most remote locations," said K P Yohannan, GFA founder and president.

"We have 200 churches located in this area. Please pray for the Lord's mercy and for our workers getting ready right now to respond to this impending crisis."

GFA disaster relief teams, which recently provided flood relief to Andhra Pradesh and Odisha, are assembling supplies for people affected by the storm.

Yohannan added: "Let us unite our hearts and cry out to the Lord for his mercy."