A top cyber-security firm is investigating whether North Korea could be linked to attacks on banks in recent months.

Symantec said it had evidence that the same group attempted to steal money from a bank in the Philippines, one in Vietnam and Bangladesh's central bank.

It also said the rare malware deployed was similar to that used in the hacking of Sony Pictures in 2014.

The US government said North Korea was behind the Sony hack.

If North Korea is found to be behind the bank attacks, it would be the first time a country has been detected stealing money in a cyber-attack, Symantec's technical director Eric Chien told Reuters.

In February this year, hackers stole $81m (£55m) from the central bank of Bangladesh.

According to Symantec, it was the same group that attempted to steal $1m from the Tien Phong Bank in Vietnam and attacked a bank in the Philippines.

In addition, the code shares similarities with malware used by the group known as Lazarus which has been accused of various attacks on the US and South Korea, including the attacks against Sony Pictures Entertainment.