Kick-off had to be delayed by five minutes owing to traffic issues around the stadium, with the United squad themselves among those caught up in the hold-ups on Tuesday.
A journey to the ground expected to take 30 minutes took more than an hour, ahead of a goalless draw that did little to lift United out of their current poor form.
And Mourinho levelled the blame squarely at the feet of local police for causing unnecessary problems for United in the build-up to the match.
"We left the hotel at 6 p.m. hoping that 30 minutes would be enough. It usually is.
"But this time the police refused to do an escort, so we came by ourselves.
"From the Lowry Hotel we took 75 minutes.
"UEFA and the referee were nice to allow the match to start five minutes late.
"It was not a problem with club organisation. We were informed that the police refused an escort."