Sanders has secured 29.7 percent of the vote in Iowa, according to his campaign's own results from almost 40 percent of the precincts in the state.
Earlier in the day, another Democratic candidate Pete Buttigieg claimed the victory.
"Iowa, you have shocked the nation. By all indications, we are going on to New Hampshire victorious. #IowaCaucuses", Buttigieg wrote on Twitter.
Tonight, an improbable hope became an undeniable reality. #IowaCaucuses— Pete Buttigieg (@PeteButtigieg) February 4, 2020
Candidates at Democratic primaries are allocated a certain number of delegates after each electoral event. After all the elections are finished, the candidate with the most delegates becomes the Democratic party's presidential candidate.
Among Republicans, three of eight winners have received the national nomination with just one, George W. Bush, eventually becoming US President.