(Adds background on Synlait and a2 Milk, share movement)
Aug 3 (Reuters) - New Zealand's a2 Milk Co ATM.NZ said on Friday it would acquire an 8.2 percent stake in Synlait Milk Ltd SML.NZ for about NZ$161.8 million ($108.9 million), prompting Synlait's shares to jump 5 percent.
The milk producer said it would acquire the stake from Japan's Mitsui & Co 8031.T for NZ$10.9 per share.
The deal comes just a month after Synlait Milk extended its supply deal with a2 Milk by two years. The companies had agreed to a supply deal in 2016 to make a2 Platinum infant formula for five years. The firms first collaborated in 2010. provides a2 Milk with products for its largest markets in Australia, New Zealand and China.
a2 Milk added that it had no plans to further increase its shareholding in Synlait
New Zealand shares of Synlait were up about 5 percent by 0024 GMT, while a2 Milk's shares rose 1.8 percent in a positive broader market .NZ50 . ($1 = 1.4857 New Zealand dollars)