LONDON/WASHINGTON (AFP/REUTERS) - Britain is sending 750 military personnel, a medical ship and three helicopters to Sierra Leone to help fight the spread of Ebola, officials said on Wednesday.

The US Pentagon is also intensifying its battle to curb its spread by sending 100 US Marines along with six aircraft to Liberia, officials in Washington said on Wednesday.

The British ship will be equipped with hospital-style critical care units while the three Merlin helicopters will carry doctors to areas where they are needed.The personnel will be deployed from next week and will help to build treatment centres, the defence ministry said.

It said 200 military personnel would be deployed to run and staff a training facility for medical workers and 250 would use the helicopters to transport supplies and doctors. The remaining 300 were already planned to assist Sierra Leone's government.

The announcement came after British Prime Minister David Cameron chaired a meeting of the Cobra emergency committee on the spread of Ebola.

The government meeting also decided to step up precautions against Ebola in Britain including through a planned "national exercise and wider resilience training".

The government said in a statement that posters would also be put up in British airports to raise awareness.

In Washington, the Pentagon said it would beef up its efforts in Africa by sending in members of a unit, based in Moron, Spain, part of a crisis-response force assigned to Africa and would despatch four Osprey tilt-rotor aircraft as well as two C-130 Hercules cargo planes to Monrovia.

Pentagon spokesman Rear Admiral John Kirby said the Marines were due to arrive in Liberia on Thursday and were sent to provide temporary help with supply efforts and air transport until troops from the US Army's 101st Airborne arrive later this week.

"We don't see this particular deployment of these Marines to be long term. It's right now considered a temporary solution to just get us some air assets in the region to deal with the austere environment that we're faced by there," he told reporters.

Kirby said the Osprey MV-22 aircraft arriving with the unit would allow troops to reach a wider area, as the Ospreys - which take off and land like a helicopter and then fly at speeds like an airplane - do not require runways.

The US military has said it plans a force of 3,200 troops in Liberia and Senegal to provide logistical and engineering support in the international fight against the deadly virus, but said it has approval to expand the mission to nearly 4,000 if needed.

The Marine unit falls within those troop plans, Kirby said.

The announcement of the deployment comes after President Barack Obama faced criticism from some aid groups over the pace of the US response to the Ebola crisis, with some questioning the timetable for the deployment of more than 3,000 American troops.

About 350 US troops are in Liberia and Senegal at the moment, setting up test labs and a field hospital for health workers. More forces are due to arrive in the coming weeks, according to the Pentagon.

American military teams trained to deal with biological threats have been deployed to Liberia to run mobile labs to test blood samples for the Ebola virus, the head of US Africa Command, General David Rodriguez, said on Tuesday.

US Secretary of State John Kerry yesterday urged more countries to "step up" in the fight against Ebola following talks with Britain's Foreign Secretary Philip Hammond.

The Ebola epidemic has killed nearly 3,900 people this year, with Liberia, Guinea and Sierra Leone worst hit.