Under pressure to avert bans of diesel vehicles in key cities, carmakers have started offering trade-in incentives to encourage customers to scrap older diesel vehicles for more modern cleaner vehicles.

A spokesman said the responsible board committee is examining a nationwide trade-in incentive for Euro 4 or Euro 5 diesel vehicles for a limited time period and is expected to make a decision early next week.

Volkswagen said in October it will offer buyers of VW-branded passenger cars an incentive if they agree to scrap cars equipped with older Euro 1 to Euro 4 engines.

The trade-in incentive is currently limited to Germany's 15 most polluted cities.

German daily Bild first reported that VW was considering extending the trade-in incentive to all of Germany. The paper said details were still being worked out but the company would pay up to 9,000 euros (£7923) per car as previously envisaged.

German carmakers have already agreed to spend up to 3,000 euros per vehicle to upgrade engine management software to make exhaust filtering systems more effective, but environmentalists say these measures are insufficient.

(Reporting by Thomas Seythal and Caroline Copley)