UPDATE AT 8.45AM
AA Roadwatch said the N7 westbound has reopened between Newlands Cross and J2 Kingswood following a serious collision last night.
A serious collision on the N7 westbound near Kingswood has caused a full closure of the route.
The major incident happened between midnight and 1am.
Motorists are being diverted through Clondalkin before re-joining the N7.
One witness reported seeing several ambulances, fire engines and Garda cars.
AA Roadwatch said:
"The N7 westbound is closed between Newlands Cross and J2 Kingswood following a serious collision."
"The outbound / westbound lanes of the N7 (Naas Road) are currently closed to traffic from Newlands Cross to Junction Kingswood following a serious collision. Diversions are in place."