"There is a two-day extension throughout the whole country," Sudan's National Elections Commission Secretary-General Jalal Mohamed Ahmed told Reuters.
"It is to give more time to the voters," he added.
South Sudan's main party on Sunday asked for a four-day extension in the south where a mostly illiterate population was grappling with 12 ballot papers and where decades of civil war had devastated infrastructure.
The complex presidential, legislative and gubernatorial polls, which began on Sunday, is aimed at transforming Sudan from a nation emerging from decades of multiple civil wars to a democracy.
After a boycott by the main opposition in the north, the vote now looks likely to confirm the 21-year rule of Bashir - the only sitting head of state wanted for war crimes by the International Criminal Court, which alleges he was behind mass murder and rape in Darfur.
Across the country - even in the capital Khartoum - voting materials were not delivered to stations, the wrong ballots arrived at many centers and opposition and independent candidates said their names or symbols were either missing or incorrect.
Many had complained and asked for an extension to the voting to compensate for the delays and resolve the problems.
