The inspections on Wednesday were meant to determine if Spain's border controls had become overly vigorous in response to a spat with Gibraltar, a small spit of sovereign British territory on Spain's southern tip.

After Gibraltar dumped several large, concrete blocks in shallow parts of disputed waters to create an artificial reef, Spain responded by saying it was detrimental to local fishing. In response, Gibraltar claims, Spain stepped up inspections at the border, contributing to long wait times for commuters who come and go on a daily basis from the small rocky territory.

Since Gibraltar is not part of the EU's passport-free Schengen area, immigration controls are carried out on the border. Spain denies that it stepped up its border presence in response to the fishing dispute. Gibraltar counters that Spain had overfished the area and the artificial reef would help restore fish stocks.

Tobacco tiff

Spain ceded Gibraltar to Britain three centuries ago in a treaty but is keen to get the territory back. In addition to the complaint over the concrete being dumped into local waters, Madrid says Gibraltar does not do enough to curb cigarette smuggling into Spain. Cigarettes are considerably cheaper in Gibraltar.

The inspectors from the European Commission were not tasked with investigating the fishing dispute, but would have a look at the claims regarding cigarette smuggling.

Gibraltar enjoys a bit of a special status in the EU. As a British territory, it is subject to EU law, but is excluded from certain areas of EU policy: the customs union, the common commercial, agricultural, and fisheries policies, and the requirement to charge value added tax on goods.

As a result, Spain is called upon to carry out checks on people and goods, but as a statement from the EU read the day before the inspections began, "these checks must fully respect EU law and remain proportionate."

mz/dr (Reuters, dpa)