The panel, led by former Tanzanian President Benjamin Mkapa, met with referendum authorities and voters in the southern Sudan states of Nile, Upper Nile and Lakes, the United Nations said in a release.
The referendum, which began Sunday and will finish Saturday, is being held in accord with the 2005 Comprehensive Peace Agreement that ended the 20-year civil war between north and south. Sixty percent of the nearly 4 million voters registered to take part in the referendum must vote for the outcome to be valid.
"We are here to witness the voting taking place and, looking at all the arrangements, I hope the people of Southern Sudan can express their will in a free and transparent manner and for a successful conclusion and peaceful acceptance of the results," Mkapa said.
Preliminary results are expected to be announced by Feb. 2 and, depending on whether court challenges are filed, the final result on whether the south secedes or remains a part of Sudan will be declared by Feb. 14, the United Nations said.