(Reuters) - Australian fintech company Airwallex said on Tuesday it raised $100 million in an extension of a funding round, sustaining its $5.5 billion valuation.

The Melbourne-based company said it secured more funds from existing investors, including Tencent Holdings Ltd, Sequoia Capital China and Lone Pine Capital.

Australian industry superannuation fund HostPlus and a North American pension fund also participated in the round, Airwallex said.

With the $100 million raised in the Series E extended round, Airwallex's total funding increased to more than $900 million, the company said.

"The market environment remains challenging in the foreseeable future, and while we remain well capitalised, this additional runway allows us to continue our growth plans," said Jack Zhang, co-founder and chief executive officer of Airwallex.

Airwallex, which allows customers to issue and pay international invoices and bills through its payments platform, said its revenue had risen 184% year-on-year, and its customer base had more than doubled.

(Reporting by Harish Sridharan and Baranjot Kaur in Bengaluru; Editing by Tom Hogue and Subhranshu Sahu)