By james art 
An apparent firebomb attack at a DHL warehouse in Birmingham linked to Russian-backed saboteurs was believed to be a test attack for a US attack, according to Polish officials.
of Poland The National Prosecutor’s Office confirmed four arrests after parcels “containing explosives” were allegedly sent via courier companies to countries including the UK.
UK Counter Terrorism Police are already investigating whether Russia had some involvement after a suspicious package caught fire at a DHL warehouse in Minworth in July.
The authorities in Germany are also investigating several fires believed to have been caused by incendiary devices hidden in parcels at a warehouse in Leipzig.
Polish prosecutor Katarzyna Kalow-Jaszewska said the latest arrests were related to parcels “that spontaneously combusted or detonated during land and air transport” to EU countries and the UK.
She said the group’s purpose was “to test the channel for the transfer of such parcels which are ultimately to be sent to the United States of America and Canada.”
She added that four people were detained who participated in “sabotage” and “of an international nature”.
On Monday, counter-terrorism police said the arrests reported by Polish authorities had not been made as part of its investigation.
This coincides with reports by the Wall Street Journal (WSJ) that the devices were “electric massagers implanted with a flammable magnesium-based substance” and “part of a wider Russian conspiracy”.
Russia has denied involvement. A Kremlin spokesman told the US newspaper that the claims were “traditional unfounded insinuations from the media”.
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A suspicious fire broke out in July at a DHL warehouse in the UK after a package arrived by air, but further details about the plane and its trajectory are not known.
Last month, British police said their investigation was being “led by officers of the The Met’s Counter Terrorism Command with the support of colleagues from West Midlands Counter Terrorism Police.”