MOSCOW, July 8 (Reuters) - Russia's second-largest cellphone operator Vimpelcom (VIP.N: Quote, Profile, Research) said on Tuesday it took a 40 percent stake in a joint mobile venture with Vietnamese state telecoms companies, and would contribute $267 million to the venture.

Vimpelcom, which announced it was setting up the venture last year, said it estimated overall investments in GTEL-Mobile, the venture, at $1.8 billion within the next five years. The company is aiming for a 15-20 percent market share in that time.

"Vietnam will be a key market for us. We will be looking for further development possibilities based on the Vietnamese operations," Vimpelcom Chief Executive Alexander Izosimov told a conference call.

Vimpelcom's partners in the venture are Vietnam's state Global Telecommunications Corporation (GTEL) and its unit GTEL TSC with 51 percent and 9 percent respectively. (Reporting by Anastasia Teterevleva; Writing by Maria Kiselyova; Editing by Melissa Akin)