Denmark has banned all civilian drone flights this week ahead of a European Union summit in Copenhagen, the country's transport minister said on Sunday. The ministry said the decision was made in order to 'simplify security work' for the police, and they could not accept 'foreign drones creating uncertainty and disruption'. Denmark is one of several European countries that have reported 'drone incidents' in recent weeks, with drones sighted above Danish military sites as recently as Saturday. Defence ministers from 10 EU countries have agreed to create a 'drone wall' in response to the sightings, and NATO says it has 'enhanced vigilance' across the Baltic. In their statement announcing the ban, the transport ministry said police were on 'significantly increased alert' ahead of this week's summit and that they needed to 'take care of Danes and our guests'. The ban will remain in place until 3 October, and violations could result in a fine or imprisonment for up to two years. Denmark currently holds the rotating presidency of the Council of the EU. Unidentified drones have been reported in Denmark since 22 September, when sightings forced the closure of Copenhagen and Oslo airports. Aalborg and Billund airports were also forced to suspend operations last week due to drone activity. Danish investigators have not yet been able to identify those responsible for the flights, but the defence minister called it a 'hybrid attack' that was part of a 'systematic operation'. Danish Prime Minister Mette Frederiksen stated that authorities are still investigating who is behind the incursions and did not rule out Russian involvement. Moscow has firmly rejected any suggestion that it was involved. The tensions in the region reflect a heightened state of alert in Europe, as several NATO countries have reported similar drone activities recently.