HANOI, Oct 26 (Reuters) - Shares of Vietnam's largest conglomerate Vingroup and its real estate unit Vinhomes fell sharply on Thursday.

Vingroup shares fell 6.94% to 41,600 dong while Vinhome shares fell 6.9% to 41,800 apiece.

"Foreign investors are offloading shares of Vingroup and its unit in what appears to be a margin call," a Hanoi-base stock broker said, adding that woes in China's properties market might have hurt sentiment.

Vietnam's benchmark stock index fell 3.8% to 1,059, the lowest since May. (Reporting by Khanh Vu)