* Flats mostly in Berlin, vacancy rate 2 percent
* 6,900 flats bought from Blackstone
* Blackstone to get 5 pct stake in Deutsche Wohnen
FRANKFURT, April 26 (Reuters) - German real estate company Deutsche Wohnen AG has agreed to buy two property portfolios comprising a total of 7,800 flats in Berlin in a deal worth about 400 million euros ($521 million).
The takeover will increase the number of apartments Deutsche Wohnen owns by 9 percent to 90,300 flats and give U.S. private equity company Blackstone Group, one of the sellers, a 5 percent stake in the company, it said on Friday.
The German group is buying 6,900 of the flats for 260 million euros in cash from Blackstone and will issue 8.15 million new shares to the U.S. private equity company, it said.
Following the deal, Blackstone becomes one of the largest shareholders in Berlin-based Deutsche Wohnen along with BlackRock and Sun Life Financial.
For the remaining 900 flats, it is paying 51 million euros in cash, Deutsche Wohnen said, declining to identify the seller.