MADRID, April 5 (Reuters) - The air appears visibly clearer in Madrid since Spain imposed some of the world’s strictest measures to tackle the coronavirus pandemic, Reuters video images show.

The measures have curbed economic activity including road transport since March 14, when the government implemented an initial 15-day lockdown, later extended to April 12.

Reuters video footage of Madrid’s skyline was taken on April 4, 2020 and in 2016.

In the images from 2016, buildings including the capital’s “four towers” skyscrapers are shrouded in smog, whereas on Saturday, the air appeared considerably clearer. Meanwhile, some of Madrid’s major roads have gone from being congested with vehicles to practically deserted.

Under the lockdown, which will now be extended to April 26, people must stay at home and leave only for essential journeys such as to buy food and medicine. All bars, restaurants and shops are closed.

Cities including Madrid, Brussels, Paris, Milan and Frankfurt showed a reduction in average levels of nitrogen dioxide over March 5-25, compared with the same period last year, according to Sentinel-5 satellite images released last week.

The images, released by the European Space Agency (ESA) and analysed by the non-profit European Public Health Alliance (EPHA), show the changing density of nitrogen dioxide, which can cause respiratory problems and cancer, like heat maps. (Reporting by Michael Gore Writing by Elena Rodriguez and Jessica Jones Editing by Frances Kerry)