Logistics giant DHL is working with Bulgarian aircraft developer Dronamics on rolling out cross-border and inter-city drones aimed at overcoming strained supply chains, executives involved say.

Global disruptions due to COVID, reduced air activity and major congestion at ports due in part to backed up container ships have upended logistics networks over the past year with companies looking for ways to ease the pressure.

DHL, which is part of the Deutsche Post DHL Group, said it was already using smaller drones to carry documents, parcels and pharmaceuticals over limited distances in Germany, Tanzania and China.

It said in an email it had partnered with UK and Bulgaria based operator and developer Dronamics with the aim of using the unmanned planes they have designed, which can carry 350 kg of cargo and have a maximum range of 2,500 km.

The first production-scale drone will be ready in October, Dronamics chief executive Svilen Rangelov said, adding it expected to be the first deployed commercially that would go beyond 100 km.

Last month, leading German freight forwarder Hellmann told Reuters it would start using the longer-range unmanned planes developed by Dronamics from next year to speed up deliveries of vital goods in Europe.

DHL said it was initially targeting Europe and Asia-Pacific and believed "now is the right time to explore this" but declined to give a time-frame for its project.

"We believe that cargo drones will be a key element in the next generation of transportation in logistics," it said.

Rangelov said Dronamics, which only flies airport to airport for now, had signed agreements with 39 airports in 13 countries in Europe and was in discussions with airports, regulators and potential customers in Australia and Canada.

German logistics company DB Schenker is working with separate developer Volocopter on a cargo drone that can transport 200 kg up to 40 km, it said earlier this month.