The benchmark index had hovered above its opening of 901.54 points for most of the day, but nosedived within the last two hours of trading as sell orders, mostly on the market’s blue chips, piled in.

According to data from brokerage VNDIRECT, shares of some of the market’s biggest caps, VIC of private conglomerate Vingroup; BID of BIDV, VCB of Vietcombank, and CTG of VietinBank, Vietnam’s three biggest state-owned lenders by assets, and six other stocks, accounted for a 11.13 decrease in the VN-Index.

The Ho Chi Minh Stock Exchange (HoSE), on which the VN-Index is based, was a sea of red with 273 tickers losing and 135 gaining. Total transaction volume was VND7.59 trillion ($327.09 million), far higher than last month’s average of VND5 trillion.

The VN30-Index for the market’s 30 largest caps tumbled 1.92 percent, with 27 stocks losing and only one gaining.

Topping losses was VPB of private VPBank, with 4.1 percent, followed by MWG of electronics retailer Mobile World, with 4 percent and SBT of agricultural firm TTC-Sugar, at 3.8 percent.

In the state-owned banking sector, CTG of VietinBank led losses with 3.8 percent, followed by BID of BIDV, with 3.6 percent, VCB of Vietcombank, 1.5 percent, and MBB of mid-sized Military Bank at 1.9 percent.

VIC of Vingroup, HoSE’s biggest cap, slid 2.7 percent this session. VRE of its retail arm Vincom Retail dropped 2.8 percent, and VHM of its real estate arm Vinhomes slumped 1.1 percent.

Other major losing tickers this session included GAS of energy giant PetroVietnam Gas, down 3.5 percent, POW of electricity generator PetroVietnam Power, down 3.4 percent, FPT of IT services giant FPT and MSN of food conglomerate Masan Group, both down 3 percent.

NVL of real estate developer Novaland and SAB of major brewer Sabeco were two that kept their opening prices this session, while VNM of dairy firm Vinamilk was the sole gainer with 0.8 percent.

Meanwhile, the HNX-Index for the Hanoi Stock Exchange, home to mid- and small-capped stocks, dropped 0.57 percent, and the UPCoM-Index for the Unlisted Public Companies Market shed 0.42 percent.

Foreign investors turned net buyers to the tune of VND50 billion on all three bourses, with buying pressure mostly on VNM of Vinamilk and the FUEVFVND, an exchange traded fund replicating the performance of stocks on the VN Diamond Index.

The VN Diamond Index is a group of 14 stocks, which includes blue chips such as TCB, VPB, MBB, MWG, PNJ, CTG and FPT. The basket of stocks, selected based on their free-float capitalization, was introduced by HoSE last November, and the FUEVFVND began trading on May 12 this year.