A church in Haiti has been destroyed and at least 11 people killed as Hurricane Matthew, the most powerful storm of kind in a decade, swept on towards Cuba, the Bahamas and Florida today.

Santification Haitian Baptist Church in St. Petersburg, Haiti was reduced to rubble, according to ABC Action News.

Bishop Josias Jocelyn of St. Petersburg said his congregation of 100 helps to support the satellite church in Haiti with donations and relief boxes of essential items. "The main problem is six years ago we were hit and they [haven't rebuilt] yet," he said.

The destruction came as the poorest area in the Western Hemisphere was hit by 145mph winds yesterday, tearing off roofs and uprooting trees in the southwestern tip of Haiti.

The full extent of damage in the area is not known because of poor communication, but there were reports of at least 11 dead.

Christian groups are mobilising in the area.

Franklin Graham announced that Samaritan's Purse, one of the world's fastest responding disaster relief organisations, is already on the ground in Haiti.

With its own warehouses and DC-8 plane, Samaritan's Purse, headed up by Graham, said it was responding within hours. The group said its objective "is to meet the spiritual and physical needs of those affected by disasters, responding in Jesus' name."

Already operating in Haiti, Samaritan's Purse has positioned shelter supplies on the ground in addition to other supplies close by in warehouses in North Carolina and Florida.

Chris Blackham, head of programmes and projects at Samaritan's Purse, said: "Hurricane Matthew has seen sustained winds of up to 140mph, covering an incredibly wide area stretching over 185 miles. Whilst we are still assessing the damage it's clear Matthew has delivered a potentially catastrophic strike to an already struggling nation.

"Samaritan's Purse is well positioned to respond, with teams on the ground since the earthquake and supplies already positioned. Right now we are encouraging Christians around the world to lift up this vulnerable nation and the whole Caribbean in their prayers".

Blackham added: "We've a real heart for this nation at Samaritan's Purse. It's a very young population and they've had more than its fair share of difficulties. For a decade our supporters have enabled us to show the tangible love of God in Haiti. We've built strong relationships with the churches in the country and we can assure people we'll be there in the aftermath of Matthew."

Samaritan's Purse has been working in Haiti since 1996.

Meanwhile, a fund has been set up to receive donations by the faith-based relief group Live Beyond.

LiveBeyond provides clean water and medical care to the region around its clinic in Thomazeau, Haiti, and said it is working to get clean water to those whose wells have flooded.

LiveBeyond founder and CEO David Vanderpool is also asking for prayer for the Haitian people, as many have been displaced from their homes and have had their livelihoods wiped out.

"Haitians are such a joy-filled, loving people who have already been through so much," Vanderpool said. "Many of them have still never completely recovered from the earthquake in 2010, and the severely damaged infrastructure makes them even more vulnerable to subsequent events such as this."

Hurricane Matthew was today heading towards the Bahamas and the US coast.

The UN has said the hurricane has brought the worst humanitarian crisis to Haiti since a devastating 2010 earthquake.

Hundreds of thousands of people were evacuated from the storm, which caused severe flooding and killed four people in Dominican Republic.

A Category 4 Hurricane throughout Tuesday, Matthew was downgraded to a Category 3 storm early on Wednesday, the Miami-based National Hurricane Centre (NHC) said.

Making it harder to assess the severity of the impact on Haiti, Matthew knocked out communications in many of the worst-affected areas, including the main bridge that links much of the country to the southwest peninsula.

There was particular concern over Haiti as tens of thousands of people are still living in tents and makeshift dwellings due to the 2010 earthquake, which killed more than 200,000 people.

Mourad Wahba, the UN secretary-general's deputy special representative for Haiti, said "much of the population" had been displaced by Matthew and at least 10,000 were in shelter.

"Haiti is facing the largest humanitarian event witnessed since the earthquake six years ago," he said.

Heifer International, a nonprofit organisation working with farming families in Haiti, said farmland and businesses caught in Matthew's path had been devastated by the storm.

The US government said it was ready to help the afflicted and around 300 US Marines set off on the USS Mesa Verde to provide disaster relief in Haiti, the Marines said in a tweet.

Initial reports from Cuban state media suggested the Communist island had not suffered especially severe damage.

Cuba's government has traditionally made extensive efforts to cope with hurricanes, and authorities spent days organising volunteers to get residents to safety and secure property.

The eye of the storm was about 35 miles north-northwest of the eastern tip of Cuba early on Wednesday, and Matthew is expected to be very near the east coast of Florida by Thursday evening after moving through the Bahamas.

Officials in the Bahamas urged residents to evacuate to higher ground, and the Ministry for Grand Bahama said on Facebook that government offices in New Providence and Grand Bahama had been closed on Tuesday until further notice.

Hurricane and tropical storm warnings were issued for parts of Florida as the storm moved north, the NHC said.

The National Weather Service said the threat to life and property was high, predicting winds of up to 70 mph and four inches of rain for parts of Florida.

Nikki Haley, the governor of South Carolina, declared a state of emergency, and ordered the evacuation of more than one million people from Wednesday afternoon.

Additional reporting by Reuters