(An aerial view of buses for Muslim pilgrims is seen in a parking lot outside Mecca December 7, 2008.  REUTERS/Susan Baaghil )

Saudi Arabia has approved a 62 billion riyal plan to modernise the transport system in its holy city of Mecca, including building a bus network and metro system, state news agency SPA said on Tuesday.

More than 6 million visitors from across the world visit Mecca every year for the Haj and Omra pilgrimages. The influx has strained the narrow roads and outdated transport system.

Four metro lines of a total length of 182 km (114 miles) will be built across the city, with 88 stations, SPA reported.

Construction for the transport project will be carried out over about 10 years, the report said, without giving details of when it would start or how companies would bid for contracts.