Police, who had been stationed outside the Electoral Commission office gates in Ntinda, escorted him immediately into custody.
Nubian Li, who was born Ali Buken, was driven away to an undisclosed location by heavily armed officers, and authorities have not yet provided details on the reason for his detention.
He had arrived at the EC offices to find heavy security, greeting the officers as he smiled and walked in.
And upon walking out, he was immediately sandwiched by the officers and Nubian Li appeared to have been aware of what awaited from way back when he arrived here.
He did not resist and was escorted into the co-driver's seat of the pickup patrol vehicle and driven away.
The arrest comes a day after Alex Mufumbiro was picked up outside Makindye Magistrate’s Court by security operatives.
Mufumbiro and other NUP members are reportedly being questioned over a military drill-like parade that took place at the party headquarters in Makerere Kavule several months ago.
Supporters of Nubian Li and other NUP members have called for clarification on the detentions, raising concerns over the treatment of political aspirants during the nomination period.