Survivors of a massive earthquake that struck Haiti on Tuesday face “untold suffering,” warns Christian Aid.

Thousands are feared dead following the 7.0 magnitude quake which struck 10 miles southwest of Port-au-Prince just before 5 p.m. local time. Buildings across the capital were toppled, including the presidential palace and the headquarters of the UN mission in Haiti. It is believed that there are no survivors inside the collapsed UN building.

Dame Anne Owers, chair of Christian Aid, said she was deeply concerned about the impact of the earthquake on already severely impoverished communities in the Caribbean nation.

“It is one of the poorest places on earth. This latest disaster is going to cause untold suffering and hardship, particularly in communities with very little to fall back on,” she said.

She said there was an urgent need for emergency supplies, including food, shelter and medicine, while in the longer-term, rebuilding would require “massive international assistance”.

“I appeal to people and to governments to give what they can,” she said.

The earthquake is the strongest to hit Haiti in 200 years and could be felt as far away as Cuba.

Three Christian Aid staff members had to be rescued after their office collapsed, although none were seriously injured. Many churches had also been completely destroyed.

Christian Aid’s Caribbean regional manager Judith Turbyne said the national response was unlikely to be sufficient because of Haiti’s weak state and the lack of resources at its disposal. She said there was a huge need for a “concerted effort” from the large aid community in the country.

U.S. President Barack Obama has promised the "full support of the United States" to the Haitians after what he called a "cruel and incomprehensible" tragedy.

"I have directed my administration to respond with a swift, coordinated, and aggressive effort to save lives," he said Wednesday. "With just a few hundred miles of ocean between us and a long history that binds us together, Haitians are neighbors of the Americas and here at home. So we have to be there for them in their hour of need."

World Vision is mobilizing staff to aid the victims but it won't be easy, staff say.

Edward Brown, World Vision’s relief director in the United States, commented, "We would be very concerned about a quake of this magnitude anywhere in the world, but it is especially devastating in Haiti, where people are acutely vulnerable because of poor infrastructure and extreme poverty."