RIYADH (Reuters) - Saudi Arabia is tightening a partial curfew imposed nationwide to contain the spread of the coronavirus, barring entry or exit from Riyadh, Mecca and Medina as well as movement between all provinces starting on Wednesday, state news agency SPA reported.

The orders, approved by King Salman, also added four hours in the three cities to the 21-day curfew that began on Monday, so that it will start at 3pm instead of 7pm as of Thursday, SPA said.

(Reporting by Maher Chmaytelli and Stephen Kalin; Editing by Hugh Lawson)