The 34-year-old forward had his contract mutually terminated by Swansea last month and his been looking for a club since then. He joins Alan Pardew's side on a deal until the end of the season.
- Download the FREE Football.co.uk iPhone and Android apps
The Magpies are currently short of strikers after the deadline day departure of Andy Carroll and the recent injury picked up by Shola Ameobi left Pardew with just Leon Best, Nile Ranger and Peter Lovenkrands to pick from.
Pardew said: "We needed another option up-front, because we're a little light there due to the temporary loss of Shola, and Shefki will provide us with something different.
"He's match fit and knows the English game well having been in the country for the best part of ten years. He is ready straight away and that's what we wanted.
"Shefki is a good, honest pro who will give us a strong physical presence from the bench."