* Liberia records most new deaths, worries over Monrovia
* WHO: "cautious optimism" over halting Nigeria spread
* Suspected cases who fled looted Monrovia centre found
* Food deliveries on their way to quarantined zones
* African medics treated with ZMapp show improvement (Adds WHO comment on Nigeria, Guinea, Liberia health ministry report, shipping companies on alert)
By Clair MacDougall and Stephanie Nebehay
MONROVIA/GENEVA, Aug 19 (Reuters)- Liberia battled on Tuesday to halt the spread of the Ebola disease in its crowded, run-down oceanside capital Monrovia, recording the most new deaths as fatalities from the world's worst outbreak of the deadly virus rose above 1,200.
The epidemic of the hemorrhagic disease, which can kill up to 90 percent of those it infects, is ravaging the three small West African states of Liberia, Sierra Leone and Guinea, and also has a toehold in Nigeria, Africa's biggest economy.
As the Geneva-based World Health Organization rushed to ramp up the global response to the outbreak, including emergency food deliveries to quarantined zones, it announced that deaths from it had risen to 1,299 as of Aug. 16, out of 2,240 cases.
Between Aug. 14-16, Liberia recorded the most new deaths, 53, followed by Sierra Leone with 17, and Guinea with 14.
On a more hopeful note, the WHO expressed "cautious optimism" that the spread of the Ebola outbreak in Nigeria, Africa's most populous nation where four deaths out of 12 confirmed cases have been recorded since July, could be stopped.
It also described the situation in Guinea, where the virus made its first appearance in West Africa in December, as currently "less alarming" than in Liberia and Sierra Leone.
The WHO said it was working with the U.N.'s World Food Programme (WFP) to ensure food delivery to 1 million people living in Ebola quarantine zones cordoned off by local security forces in a border zone of Guinea, Liberia and Sierra Leone.
"Providing regular food supplies is a potent means of limiting unnecessary movement," it said in a statement.
Besides infection in border zones, Liberia is fighting to stop the spread of the virus in the poorest neighbourhoods of its capital, such as the West Point slum where at the weekend a rock-throwing crowd attacked and looted a temporary holding centre for suspected Ebola cases, 17 of whom fled.
As fears of wider contagion increased - Ebola is spread by contact with the bodily fluids of infected persons - Liberia sent police to track down the fugitive suspected cases.
"We are glad to confirm that all of the 17 individuals have been accounted for and have now been transferred to JFK Ebola specialist treatment centre," Liberia's Information Minister Lewis Brown told Reuters on Tuesday.
He added that after meetings with religious and community leaders, a task force was being set up to go door-to-door through West Point, a labyrinth of muddy alleys, to explain the risks of the disease and the need to isolate infected patients.
"I know that Monrovia is really of concern to WHO," WHO spokeswoman Fadela Chaib said in Geneva.
Lewis said the Liberian authorities were considering imposing even tougher restrictions on movements.
Liberia and Sierra Leone's weak health systems have been overwhelmed by the multiplying numbers of cases and deaths.
WHO has said it is coordinating a "massive scaling up" of international assistance to the worst affected countries.
But a Liberian health ministry report for Aug. 17 said its Ebola-hit Lofa County had stopped burials due to a lack of body bags. "Absolutely no body bags," the report said.
It said the ministry warehouse had only three pairs of rubber boots remaining and no more bottles of hand sanitizers.
"I am sorry to say the government has lost the fight against Ebola. It is out of control now," said student Samuel Zorh.
On Friday, the Liberian and Sierra Leonean governments and a medical charity chided the WHO for its slow response, saying more action was needed to save victims threatened by the disease and hunger.
"IMPROVEMENT" AFTER RARE DRUG USED
The WHO declared the West African Ebola outbreak a "public health emergency of international concern" on Aug. 8, triggering global alarm as countries stepped up precautions and testing.
Reflecting this, emergency services in Berlin on Tuesday cordoned off a job centre and took a woman with Ebola-like symptoms including high fever to hospital.
The U.N. health agency this month gave the green light to use untested pharmaceuticals to treat Ebola patients.
In Monrovia, three African healthcare workers were given the rare experimental ZMapp drug, which has already been used on two American aid workers being treated in the United States after being evacuated from Liberia with Ebola.
Lewis said the three Africans treated with ZMapp were showing "remarkable signs of improvement".
However, the manufacturer of the drug, California-based Mapp Biopharmaceutical, has already said its scarce supplies have been exhausted. Officials have cautioned the public not to place too much hope in untested and scarce treatments.
As part of the increased international response, WFP is stepping up emergency food deliveries to the quarantined areas, which include severely-affected cities such as Gueckedou in Guinea, Kenema and Kailahun in Sierra Leone and Foya in Liberia.
Fears of the disease and quarantine measures like military and police roadblocks have stopped farmers from reaching their fields, and as a result food output has dropped, raising fears that a famine could set in on top of the deadly illness.
"We think that even beyond the control of the outbreak there will be severe food shortage," said Gon Myers, WFP country director for Sierra Leone. The extra food deliveries would be trying to reach 400,000 people in Sierra Leone alone.
The WHO has told countries affected by the outbreak to screen people departing at airports, seaports and major land border points and stop any with signs of the virus.
It has argued against further travel restrictions, but several international and regional airlines have cancelled services to Liberia, Sierra Leone and Guinea.
Shipping companies operating on Africa's west coast, as well as port authorities, were also on high alert.
"We sense a certain amount of concern out there in the industry," Ian Millen, Chief Operating Officer of Dryad Maritime, a maritime operations company, told Reuters, but he said he had not seen widespread cancellations of services.
Nigeria said on Monday its confirmed Ebola cases had reached 12, up from 10 last week, but five had almost fully recovered. Four people have died from the virus in Lagos, where it was transferred by a U.S. citizen who arrived by plane from Liberia.
Although WHO said the situation in Lagos looks "reassuring", Cameroon closed its borders with Nigeria on Tuesday as a precaution. (Additional reporting by Emma Farge in Dakar, Alphonso Toweh, Josephus Olu Mammah in Freetown, Tansa Musa in Yaounde and Wendell Roelf in Cape Town.; Writing by Pascal Fletcher; Editing by Anna Willard)