xperia sp power on

[orges]

I was using my XPERIA SP and suddenly it shut down. 
I tried to turn it on but i couldnt. 
I tried to use the OFF button , still no sign.

My battery was 70 % when it happened.

I tried connecting with pc but still doesnt work. 

What to do ?

Please help me. 
I dont have a sony service center near me. 

[Thommo]

Try holding both the volume up and power buttons for around 10 to 15 seconds then try restarting your device or remove the back cover and near the bottom is a recess with the word OFF you will need a pin or something to depress the button and again try restarting your device

[orges]

Im charging now. Tried that with volume up and power button and no vibration. 
I press the OFF button on the back but nothing happens. Maybe it is a battery problem ?