BNP Paribas has agreed to buy the Belgian state's 25 percent stake in BNP Paribas Fortis for 3.25 billion euros ($4.36 billion), the French bank and the Belgian government said in a joint statement on Wednesday.

The Belgian state will make a capital gain of about 900 million euros following the closing of the deal, the parties said.

The deal will have a negative impact of about 50 basis points on BNP Paribas' Basel III core Tier 1 ratio and a positive effect of about 3 percent on earnings per share in 2013, they said.