Suspicious envelopes sent to foreign missions in Istanbul

One person who opened the envelope at the Canadian mission was directly exposed to the unknown substance, which was now being analysed by experts, Turkey's disaster management agency AFAD said.

The consulate has been shut down for one day over security concerns, a Canadian embassy official told AFP. There was no immediate claim of responsibility but the incident came amid mounting concerns about the growing national security threat posed by militants returning from war-ravaged Syria and Iraq.

Canada has been hit by two deadly attacks this week -- a hit-and-run assault and a shooting at Canada's war memorial and parliament building. Canadian officials said the two men accused of carrying out the separate attacks had recently converted to Islam and wanted to join the extremist fight.

The AFAD said experts quickly intervened at the Canadian consulate after the discovery of the suspicious envelope.

"One person who opened the envelope was directly exposed to the substance and six others were indirectly exposed," it said, without making clear whether they had become ill.

"The envelope was sent to the laboratory to be analysed and see what the powder was ... and was subjected to the necessary treatment."

AFAD radiology experts donning white protective suits were seen carrying green bags as the police sealed off the area. An AFP reporter said the experts had left the Canadian consulate and were on their way to the Belgium and German missions.

Turkey has a long and porous border with Syria stretching from the Mediterranean to Iraq which has made it the main transit point for foreign rebels seeking to fight the Syrian regime.