West Yorkshire Police tweeted just after 11.30am that the road was closed due to the "serious" collision.
The route is closed in both directions between Armley Gyratory and the M621 junction 2, Leeds Travel Info said.
More follows.
Crash closes A643 in Leeds
Emergency services are attending a serious crash which has closed the A643 in Leeds.
By The Newsroom
Saturday, 9th September 2017, 1:36 pm
Updated Monday, 11th September 2017, 12:31 pm