Officials in the state of Baden-Württemberg, of which Stuttgart is the capital, said on Tuesday the new measure was intended to reduce diesel emissions that are harmful to human health.

The decision, which will be introduced in 2018, would allow the state government to ban diesel cars from entering the city during periods of high pollution.

Only those cars that meet the Euro 6 emissions standard - the most stringent set of EU targets for diesel emissions, introduced in 2014 - will be allowed to use the city's busiest roads on days when a poor air quality warning has been issued. Roughly one in 10 diesel cars currently on German roads meet these targets.

The measure comes days after London announced it would introduce a new 10-pound (12-euro, $12.50) fee for more polluting cars to drive in the center of the British capital, and follows plans for a complete ban of all diesel vehicles by 2025 in Paris, Mexico City, Madrid and Athens.

Location doesn't help

Stuttgart, an industrial city located in the bowl-shaped Neckar valley, regularly reports particulate levels from diesel vehicles above the EU's designated safe levels.

Officials said speed limits would also be tightened, public transport improved and new cycle lanes introduced in the 600,000 population city.

Stuttgart, which is home to German automakers Mercedes-Benz and Porsche, last issued an air pollution alert on January 9, when 78 micrograms per cubic meter of fine particulates was recorded in the city's air. EU regulations set the limit at 50 micrograms.

Germany's federal environment ministry acknowledged that high pollutant levels were an issue in several cities, but described the Stuttgart measures as "particularly complex," adding it would prefer other solutions to be implemented.

Environment Minister Barbara Hendricks (SPD) had recommended a system of blue badges for low-polluting vehicles, but the plan has been met with resistance.

The Berlin government has also announced plans to introduce 6 million electric cars by 2030.

EU fines threatened

But Germany has faced repeated warnings from Brussels over the levels of fine particulate matterin the air, which can cause cancer in the long term. The high levels in Germany are generally attributed to the large number of diesel vehicles on the roads.

The European Commission threatened fines after it repeatedly found limits for the pollutant were exceeded in 28 areas of the country, including Berlin, Munich, Hamburg and Cologne.

The issue has also extra received attention since the country's Volkswagen auto brand admitted that its diesel motors had been rigged with software to trick emissions tests.

mm/msh (AP, dpa)