He was born in Tura.[1] His international breakthrough came at the 1971 European Indoor Championships in Sofia. All three medalists jumped 2.17, and Kelemen got the bronze medal on countback.[2] At the 1975 European Indoor Championships, Kelemen won the silver medal with a jump of 2.19 metres. He was two centimetres behind gold medallist Vladimír Malý, but beat Rune Almén, Aleksandr Grigoryev, Paul Poaniewa and Rolf Beilschmidt, who all achieved 2.19, on countback.[3] At the 1975 European Indoor Championships, Major only managed a sixteenth place, jumping 2.13 metres.[4] He competed at the 1976 Summer Olympics, but did not reach the final round.[1]
Kelemen became Hungarian high jump champion in 1970, 1971, 1974 and 1975, rivalling with Ádám Szepesi and István Major.[5] He also became indoor champion in 1974, 1975 and 1976.[6]
His personal best jump was 2.23 metres, achieved in 1976.[1]
