Brazilian Nightshade

Your close! the flowers are wrong for Solanum seaforthianum. seaforthianum has very similar fruit as well but if you look close -especially at the flowers- you can see that this is indeed Bittersweet; Solanum dulcamara. The easy way to I.D. dulcamara is to see that the petals are reflexed (as opposed to the more cup like shape of seaforthianum), and that near the stamens are small white-green dots.
Excellent photos by the way!

It happens sometimes when we are very sure of an answer. It always happens to me. I have a small herbarium and I simply write the details of the plant with my previous knowledge but when later I give it to someone to cross check I find out that I was totally wrong about simple facts like this.

I think you nailed it namithahelen, well done and Thank you. :)

This flower does not seem to be that of Atropa and the fruit of A.belladona is more rounded. The plant in this photo have greater resemblance to wild brinjal [eggplant] . I can be totally be wrong because wild eggplant and Atropa are in the same family Solanaceae.
I think it is Brazilian Nightshade (Solanum seaforthianum) http://en.wikipedia.org/wiki/Solanum