npm publish causes 'Error: EPERM: operation not permitted, unlink ...', errno -4048

I'm trying to publish my NPM package: npm publish.

I get the following quite cryptic error:

npm ERR! path c:\Temp\npm-20936-b98f84c8\tmp\fromDir-02dd5394\package.tgz
npm ERR! code EPERM
npm ERR! errno -4048
npm ERR! syscall unlink
npm ERR! Error: EPERM: operation not permitted, unlink 'c:\Temp\npm-20936-b98f84c8\tmp\fromDir-02dd5394\package.tgz'
npm ERR!     at Error (native)
npm ERR!  { Error: EPERM: operation not permitted, unlink 'c:\Temp\npm-20936-b98f84c8\tmp\fromDir-02dd5394\package.tgz'
npm ERR!     at Error (native)
npm ERR!   cause:
npm ERR!    { Error: EPERM: operation not permitted, unlink 'c:\Temp\npm-20936-b98f84c8\tmp\fromDir-02dd5394\package.tgz'
npm ERR!        at Error (native)
npm ERR!      errno: -4048,
npm ERR!      code: 'EPERM',
npm ERR!      syscall: 'unlink',
npm ERR!      path: 'c:\\Temp\\npm-20936-b98f84c8\\tmp\\fromDir-02dd5394\\package.tgz' },
npm ERR!   isOperational: true,
npm ERR!   stack: 'Error: EPERM: operation not permitted, unlink \'c:\\Temp\\npm-20936-b98f84c8\\tmp\\fromDir-02dd5394\\package.tgz\'\n    at Error (native)',
npm ERR!   errno: -4048,
npm ERR!   code: 'EPERM',
npm ERR!   syscall: 'unlink',
npm ERR!   path: 'c:\\Temp\\npm-20936-b98f84c8\\tmp\\fromDir-02dd5394\\package.tgz' }
npm ERR!
npm ERR! Please try running this command again as root/Administrator.

Tried running as admin - same error.

NPM version: 5.4.0

Node version: 6.11.1

OS: Windows 10

Any leads?