A man allegedly ran at police with a samurai sword before being shot in the chest by Queensland police.

The incident happened in Brisbane's northwest at Ashgrove's Glenlyon Drive about 8.30pm on Thursday.

The man was still in a critical condition at Royal Brisbane and Women's Hospital at 7.30am Friday.

Police have set up a road block, cordoning off about 400m around the scene where they say the man had threatened officers responding to reports of a domestic dispute.