Angry farmers from Fukushima brought a large cow to the centre of Tokyo Friday to demand Japan's government investigate a disease they say cattle have developed since the nuclear disaster three years ago.

Operators of non-profit "Kibo no Bokujo", or "Farm of Hope", delivered a full-size black cow to the front of the agriculture ministry to demand an investigation into why it and many other animals have developed white dots on their skin since reactors went into meltdown after the earthquake and tsunami of March 2011.

The farm is located only 14 kilometres (nine miles) from the nuclear plant and is keeping some 350 cows that were abandoned in the area when their owners had to evacuate because of radiation contamination.

"Our cows cannot be shipped as meat. They are evidence of lives affected by radiation," said Masami Yoshizawa, leader of the farm, in front of the ministry, as his supporters and media looked on.

Fellow Fukushima farmer Naoto Matsumura said: "What if this started happening to people? We have to examine the cause of this and let people know what happened to these animals."

The vast farmland in Fukushima has been contaminated by radioactive materials from the Fukushima plant, forcing tens of thousands of local residents to give up their homes to live in temporary shelters.

The government says it could take decades to clean the region, but scientists say many residents may never be able to return because of the contamination.