Twitter Inc (TWTR.N) said it plans to raise $1.3 billion by issuing convertible senior notes, its first debt offering since its market debut in November.

Twitter shares fell about 1.5 percent in extended trading on Wednesday.

The company plans two offerings worth 650 million each in convertible senior notes due to mature in 2019 and 2021, the microblogging website said in a filing.

Twitter will also grant initial purchasers an option to buy up to $100 million in each of the offerings.

The San Francisco-based company said it would use part of the net proceeds for general corporate purposes.