Nigeria, May 26 -- Former Vice President Atiku Abubakar has taken an early lead in the African Democratic Congress (ADC) presidential primary as collation of results from Tuesday's nationwide exercise continues, amid reports of irregularities and factional tensions that complicated the process.

The direct primary, conducted across 8,809 wards in the 36 states and the Federal Capital Territory, follows the collapse of consensus talks among the aspirants. The candidates are Atiku, former Transportation Minister Rotimi Amaechi, and economist Mohammed Hayatu-Deen.

Preliminary results from several states, according to party officials and state-level tallies, indicated that Atiku was winning with wide margins.

In Sokoto State, Atiku polled 6...