With more than 70% of results declared the ANC has 42% of the vote.
The party had always polled above 50% in all elections since 1994.
If current trends persist the ruling ANC could fail to win its first parliamentary majority in 30 years.
The Democratic Alliance is second with 23%.
The new party, MK, led by ex-President Jacob Zuma has done very well in his heartland of KwaZulu-Natal.
Nationally the MK party has 12% of the vote and is currently third overall.
If it fails to reach reach 50%, the ANC will have to form a coalition government with one one or more smaller parties
The distribution of seats in the 400-member National Assembly directly reflects the vote share.
In order to get a parliamentary majority it looks like the ANC will need to form some sort of coalition.
The party has never been in this position before and this vote heralds a new era in South African politics.
Political deals will be made behind the scenes, but the ANC could be open to power-sharing with the DA and IFP.
Fractious relations with ex-President Jacob Zuma may make a deal between his MK party and the ANC unlikely.
A regional swing in KwaZulu-Natal province sees the MK party win twice as many votes as the ANC.
Voters canvassed in a survey were mostly content but some said long queues undermined their trust.
