VIENNA/OSLO, March 23 (Reuters) - The release of two types of radioactive particles in the first 3-4 days of Japan's nuclear crisis is estimated to have reached 20-50 percent of the amounts from Chernobyl in 10 days, an Austrian expert said on Wednesday.

The calculations published by Austria's Central Institute for Meteorology and Geodynamics may add to growing concern in Japan and elsewhere over the contamination of food products such as milk and vegetables in areas near the Japanese reactor site.

On Tuesday, France's IRSN radiation protection and nuclear safety institute estimated that leaks of radiation from the Fukushima plant crippled by the March 11 earthquake and tsunami represented about 10 percent of those from Chernobyl, the world's worst nuclear disaster, in 1986.