Six U.S. senators have urged President Barack Obama to prioritize cybercrime at this weekend's Group of 20 summit in China, in the wake of the theft of $81 million from Bangladesh's central bank, according to a letter obtained by Reuters.

In the letter sent to the White House ahead of the Sept. 4-5 summit, Sen. Sherrod Brown, a senior Democrat on the Senate Banking Committee, and five other Democratic senators say they want the U.S. president to press leaders from the world's 20 biggest economies to commit in joint communiques to a "coordinated strategy to combat cybercrime at critical financial institutions."

The letter, dated Monday, suggests that concern among U.S. lawmakers is growing over the February incident in which hackers breached Bangladesh Bank's systems and used the SWIFT banking network to request nearly $1 billion from an account held at the Federal Reserve Bank of New York.