Reports continue to unfold of the massive destruction caused by Tuesday's earthquake in Haiti, which left thousands in the impoverished Caribbean nation dead, injured and homeless.

The International Red Cross reported that nearly 3 million Haitians, approximately one third of the country's population, have been affected by the quake, which is considered to be the worst tremor to hit the nation in nearly 200 years.

"The tragedy in Haiti is unbelievable – the pictures of the pain and destruction are haunting. My heart breaks for the families and the victims of this tragedy," wrote Sojourners President Jim Wallis, writing on his blog from Los Angeles.

The 7.3 temblor flattened the country's capital city of Port-au-Prince, destroying most of its already weak infrastructure including roads, homes, office buildings and hospitals, as well as the residence of Haitian President Rene Preval.

A report from Christian Aid's Caribbean regional manager Judith Turbyne estimated that 97% of the housing and flats in Port-au-Prince had collapsed in the quake.

"Bearing in mind the very flimsy state of much of the housing in the poorer areas of the city, the overall damage in terms of infrastructure and loss of lives is likely to be very severe," Turbyne wrote in a statement released on Christian Aid's website.

"It is the most difficult kind of emergency; one that touches the lives of those who are charged with responding."

"The support, understanding and care from those of us not directly touched by the pain of the disaster are of great importance."

Churches in the area were also heavily affected, according to reports from Episcopal missionary the Rev. Lauren R. Stanley who detailed the "terrible news" on her blog.

"There is no Cathedral. The entire Holy Trinity complex is gone. The convent for the Sisters of St. Margaret is gone. The Bishop's house is gone. College St. Pierre is gone. The apartment for College St. Pierre is still standing. [The] Bishop no longer has a house in which to live," Stanley said.

"In Trouin, four people were killed during a service. In Grand Colline, the church is gone. In St. Etienne, the church is gone."

The quake also hit the Roman Catholic archdiocese's offices in Port-au-Prince, where Archbishop Monsignor Joseph Serge Miot was found dead on Wednesday.

An e-mail to the Catholic News Service reported that Miot "was hurled from the balcony outside his room while he was waiting for another person on their way to a ceremony. The force of the earthquake threw him headfirst off the balcony and he died, it seems, from the impact."

The 63-year-old clergyman was remembered as a "humble" man and "very close to poor people in Port-au-Prince" by his colleagues.

"He was such a wonderful man," said Liz McDermott of Le Claire, Iowa told the Catholic News Service. "We lost a wonderful soul, truly a man of God. It's just heartbreaking."

The total number of casualties from the quake remains unknown, although officials have made estimates ranging from 20,000 to 100,000. President Preval told CNN that he fears several hundred thousand people have been killed by the quake.

Search and rescue efforts became top priority for relief workers in the region on Friday as they approached the critical 72-hour mark after the quake's initial hit – a time period that experts say is when most deaths from earthquakes occur.

"Basically, how long can people survive under tons of rubble without water, without food?" Ian Bray, senior press officer for humanitarian agency Oxfam, asked CNN on Friday.

"Water is the key thing," Bray said. "You can go for some time without food, but you can't go all that long without water."

In a statement released on Thursday, Archbishop of Canterbury Rowan Williams said that he was "profoundly shocked and concerned" upon hearing about the extent of the damage in the tragedy, and urged the public to "hold the people of Haiti in their prayers, and to give generously and urgently to funding appeals set up for relief work."

"We stand alongside all the people in Haiti affected by this terrible disaster in prayer, thought and action as the situation unfolds," Williams said.

"We pray for the rescue of those still trapped and look towards the rebuilding of lives and communities."