Two letter bombs went off in two Dutch cities early on Wednesday, local police confirmed. 

One parcel exploded in the capital Amsterdam after being received in the mail room of a company in the northwestern area of the city, at 8.00 a.m. local time (0700 GMT).

None were injured in the attack, Amsterdam police announced on Twitter.

A second blast hit Kerkrade, southern-most province of Limburg.

"A letter package exploded at a postal sorting company on Wiebachstraat in Kerkrade around 8:30 am [0730 GMT]. No one was hurt," said the Limburg police on Twitter.

The building was evacuated and police investigations are ongoing, it added.

"It is still unknown whether there is a connection with the explosion of a letter package this morning in Amsterdam," said the Limburg police.