* August group sales down 5.4 pct vs 3.7 pct decline in July
* Monthly VW brand sales down 8.1 pct
* VW cites tough Latin America, Russia, China (Adds figures for VW brand, January-August period)
FRANKFURT, Sept 18 (Reuters) - The decline in Volkswagen's group vehicle sales accelerated to 5.4 percent in August, from 3.7 percent in July, with the German carmaker citing tough markets in Latin America, Russia and China.
Deliveries at the 12-brand group, which includes luxury division Audi and sports-car maker Porsche, came in at 714,400 vehicles, VW said on Friday.
In April, Volkswagen group sales fell for the first time in at least four-and-a-half years, raising pressure on the German carmaker to fix trouble spots laid bare by the shock ouster of Chairman Ferdinand Piech.
Core brand sales, which account for 60 percent of group deliveries, slumped by 8.1 percent in August, compared with a 6.9 percent decline in July.
The group did not break out regional sales figures for the month of August but said that VW brand deliveries in Brazil slumped by about 31 percent to 240,100 vehicles in the first eight months of 2015, while sales were down 8.1 percent at 1.68 million in China and down 42 percent at 49,100 in Russia.
Last month, it had said January-to-July brand sales were down 29 percent in Brazil, 7.7 percent in China and 44.3 percent in Russia. (Reporting by Maria Sheahan; Editing by Noah Barkin and Elaine Hardcastle)