Rail closures across Auckland and Wellington begin today to allow major network upgrades across the weekend

All services will resume on Monday for Wellington, and on Tuesday in Auckland.

Buses will replace all passenger services for both cities - excluding the Wairarapa Line, where trains will operate between Masterton and Upper Hutt.

Kiwirail's David Gordon says it will result in lasting infrastructure upgrades and maintenance.

He says the work in Auckland will ensure the network can be maintained once the City Rail Link opens.