Renewal of (M) type Business and Trade type

Hi, i am currently situated in Xiamen with an (M) type Chines Business and Trade one that was provided to me by the Chinese consulate in India. However, my Internship at a company here requires me to stay for a duration of at least 6 months and i have the Invitation letter mentioning the same to justify my position. So is it possible for me to get an extension from within mainland or must i have to return to my country of origin i.e INDIA to reapply for the same.
Also please let me know as to what i might opt for when i reapply i.e (either one applicable for 3 months and then reapply for that again or directly apply for a 6 months one if such a thing is available ).
I urgently need help regarding this as i only have a fortnight left in my current one and also this Internship is extremely important for my career, Please help me solve this dilemma.
Thanks in advance for your kind support.