I'm trying to lose weight (or fat) but also want to put on some muscle. Will weight training work against weight loss? Lost around 13 kilo so far.

No. The term losing weight is imprecise. What you want to do is loose fat.Weight training and building muscle will help you loose fat and at the same time help to reduce the loss of muscle that accompanies caloric restriction. Not only will you burn more calories during weight training but muscles burn more calories than fat even when you are at rest. See> http://bbcom.me/1Kt7vbI.
Use weights. When on a diet for exercise, you should incorporate both weight training, as well as cardio. Weight training may actually help lose weight quicker than cardio alone. It will also provide your arms and thighs with a nice toned appearance that most people find attractive. In addition to exercise, be sure to keep track of your calories and limit calories to what is recommended for your size.