Police Tuesday morning fired teargas at the Forum for Democratic Change (FDC) offices in Najjanakumbi.
The situation remained tense as officers surrounded the offices and laid a siege.
The Leader of Opposition Betty Awol Ochan was also barred from accessing the offices ahead of the nomination of their candidate.
Ochan says she doesn’t know where their party president Patrick Oboi Amuriat is.
Ochan was denied entry to FDC headquarters.
Meanwhile, Patrick Amuriat was arrested by Uganda police and driven to Kyambogo nomination centre.
Police deployment at the FDC headquarters in Najjanankumbi, Kampala remains tight.
No one is allowed to access the premises, supporters and party officials have been turned away.