The moves are the latest in what one analyst called an "increasingly desperate" battle for circulation.
The one-off price cut comes in the middle of a two-to-three week newsprint delivery problem, first reported last week, which forced News International to cut pages and reduce print runs, limiting the amount of advertising it could accept.
A spokeswoman said the group's newspapers were still ahead of budget for advertising lineage and expected supply to return to normal within a few weeks.
The company would not confirm whether it was offering to buy newsprint at large premiums from "spot" market suppliers, as widely rumoured yesterday. The Telegraph Group, also the subject of market rumours, said it had no supply problems.