lock UIImagePickerController in Portrait mode in ios app

Question

In my IOS app, when I open the camera I have placed an image over the camera view. It looks good in portrait mode. But when it is changed to landscape mode it looks some odd. So I want to lock the UIImagePickerController in Portrait mode.

Following is my code for ui image picker controller

UIImagePickerController *imgPkr = [[UIImagePickerController alloc] init];
imgPkr.delegate = self;
imgPkr.sourceType = UIImagePickerControllerSourceTypeCamera;

How it can be locked in portrait mode....