AMMAN/ISTANBUL, April 4 (Reuters) - Turkey scoped out at least three air bases in Syria where it could deploy forces as part of a planned joint defence pact before Israel hit the sites with air strikes this week, four people familiar with the matter said.

The bombardment signals the risks of a deepening rift between two powerful regional militaries over Syria, where Islamist rebels have installed a new government after toppling former leader Bashar al-Assad in December.