Camera Rotation using Left, Right,Up ,Left buttons

I am using PointerControl.js controls and all work fine, but when I click on my UP button, i do control.getObject().rotateX(0.001) and same with Left and Right button , i do control.getObject().rotateY(0.001) , it will not maintain horizontal level, can anyone help me out in this?

Can you provide a jsfiddle illustrating your issue? You can adapt this one:

replacing orbit controls with pointer controls.

Thanks for the help, it works