The weakness of the Turkish lira has placed an extra 11 billion lira ($3.82 billion) burden on Turkey's natural gas bill since the beginning of the year, Energy Minister Taner Yıldız said on Wednesday.Speaking to journalists in the Turkish capital Ankara, Yıldız said there had been an 8 percent drop in Russian gas sales to Turkey in the last 5-6 months, without giving further details. He also stated he had sent a draft inter-governmental agreement to Russia on the proposed Turkish Stream project, and was awaiting a response.