safari request timeout from gstatic

My setup

OS X 10.11.2 (15C50)

Safari Version 9.0.2 (11601.3.9)

MacBook Pro (Retina, 15-inch, Late 2013)

I experience long webpage load times when accessing goole.com, hangouts.google.com or youtube.com

I get similar behaviour from my local web app project when webpage tries to access gstatic.com

The requests timeout eventually and the page stays half loaded without texts or images. No similar problem observed on Firefox. Any suggestion to solve the problem?