German security authorities on Friday warned of "unconventional incendiary devices" being sent in parcels via freight service providers.

The DPA and Reuters news agencies cited an alert from the Federal Criminal Police Office (BKA) and the BfV domestic intelligence agency. 

The alert, which was sent to logistics and aviation companies, described several incidents in which parcels sent by private individuals in several European countries caught fire while in transit.

The agencies said they had been aware of the issue for several weeks.

"Based on the current status, it can be assumed that the unconventional incendiary devices were sent intentionally to damage freight service companies and other logistics infrastructure," the alert continued.

The agencies added that it was possible that other such packages were in circulation.

While Russia is not mentioned in the warning, security sources told DPA that authorities have not ruled out a possible connection with increasing cases of Russian sabotage in Germany.

Parcel fire spread to entire container

Security sources said the warning is linked to an incident at the DHL logistics center in the eastern German city of Leipzig, which acts as the company's global hub. 

A parcel sent from the Baltic States containing an incendiary device is said to have caught fire there in July.

The parcel is said to have set fire to an entire freight container, which also contained other parcels, but the fire was extinguished quickly. 

Responding to a request, logistics giant DHL said it was aware of two such incidents within its network, adding that it was treating the alert seriously:

"In response to the ongoing investigations by authorities in several countries, DHL Express has taken measures in all European countries to protect its network, its employees and facilities as well as its customers' shipments. We are aware of two recent incidents involving shipments in our network."

The company said it is cooperating fully with the relevant authorities.

mm/rc (dpa, Reuters)