Malaysia's government has summoned Singapore's high commissioner for talks, saying it was "extremely concerned" by reports the city-state helps Western intelligence agencies spy on the region.

Media reports citing documents leaked by former US National Security Agency (NSA) contractor Edward Snowden put Singapore - a key US ally - at the centre of a spy network that reportedly taps undersea cables.

Citing documents leaked by Mr Snowden, Australia's Sydney Morning Herald said Singapore military intelligence helped US, British and Australian spy agencies harvest data passing through a major undersea cable called SEA-ME-WE 3, which is part-owned by Singapore Telecommunications (SingTel).