The explosion took place on Thursday, when a suicide bomber staged the attack near the entrance to President Bashar Assad’s
ruling party offices.
Brahimi said he "strongly condemns the savage and horrible explosion in Damascus yesterday, which resulted in the killing of around 100 and the injuring of two hundred fifty civilians.
"Nothing could justify such horrible actions that amount to war crimes
under international law," Brahimi added in a statement.
Brahimi called last month for the UN Security Council
to set up an independent international investigation for “such crimes” in Syria.
Assad’s government and the opposition have blamed the Damascus attack on “terrorists.”
Syria has asked the United Nations to issue a clear condemnation of the bombing in Damascus.
In letters to the UN Security Council, the Syrian Foreign Ministry said that the adoption of a firm stance on the deadly attack "would send a message to terrorist groups and those who support them.
"(…) But if the UNSC turns a blind eye to this terrorist act, just as it did previously, it will deepen doubts about its seriousness in combating terrorism and its commitment to implementing its resolutions in this regard,” the letter said.
The UN's Human Rights Council believes some 70,000 people have been killed since the Syria crisis began in March 2011.