Thousands of people made homeless by Bangladesh's deadliest cyclone in 16 years scrambled for cover after rumors spread that a tsunami was about to hit the devastated coastline, officials and reporters said on Friday.

People squatting under the sky for a week after the cyclone killed thousands began running to and fro, looking for safe grounds on Thursday night to escape the unfounded tsunami, said a journalist in the coastal Barisal district.

No one knows who spread the false alarm, and why, that followed a rise in water levels at sea and rivers, journalist Aroop Talukder said.

Weather officials said it was just a normal high tide, but it scared traumatized cyclone survivors many of whom are still not getting any relief a week after the November 15 cyclone, due to horrendous logistical difficulties and the scale of devastation.

As the scare died down at dawn on Friday, thousands of people were seen lining up along highways waiting for relief trucks to come by, said Reuters cameraman Rafiqur Rahman in Swarankhola, an area badly mauled by the cyclone.

Men, women and children also crowded on the river banks and often ran into the water to grab food packets handed by government and private relief operators, he said on Friday.

Cyclone Sidr killed around 3,500 people and left thousands injured or missing, officials said. In some areas, the survivors were still retrieving human and animal corpses, they said.

Another 2 million people have been displaced, officials and aid workers say.

COLD AND FOG

A massive military-led relief operation is under way to provide food, medicine, clothes, blankets and safe water to survivors that has been pouring in from all over the world.

Countries, institutions and charities have offered $200 million in aid so far.

Survivors are collecting whatever they can from their devastated homes to build shelters, especially to protect them from early winter cold and fog, adding to their misery from hunger and disease.

Bangladesh's army-backed interim government said two U.S. C-130 cargoes planes will help the Bangladesh air force deliver supplies to remote areas in a day or two, and two U.S. Navy ships carrying helicopters and marines will arrive over the weekend.

We are about to mount a very big and well-coordinated relief effort shortly, said one disaster management official.

Cyclone Sidr was the strongest since a 1991 cyclone killed around 143,000 people.

Officials and experts say a much better cyclone preparedness and advance warning system helped save thousands of lives this time.

As responses to disasters have improved, and as some shelter infrastructure has been put in place, death tolls have become smaller, said Xian Zhu, World Bank Country Director in Bangladesh. But Bangladesh remains extremely vulnerable, the more so as climate change adds to its burden,

Preliminary estimates show more than 5 million people in 30 districts were affected by the storm. Half of them need life-saving emergency assistance for the next two to three months, said Elisabeth Byrs, spokeswoman of the U.N. Office for the Coordination of Humanitarian Affairs (OCHA).

(Additional reporting by Ruma Paul; Editing by Bill Tarrant)

Tsunami