The US-based SITE Intelligence Group stood by its reports on the Islamic State's (IS) claims of the responsibility for the killings of two foreigners and bomb attacks on Shia headquarters in the country.

"The claims have been authenticated and found credible by SITE's rigorous verification process," the for-profit Maryland-based company, which tracks online activity of White supremacist and jihadi organisations,  said in a press release yesterday.

The statement came in view of Bangladesh government's denial of existence of IS after SITE reported the terrorist group claimed responsibility for the murders and bomb attack in Dhaka and Rangpur.

Rita Katz, director of SITE Intelligence Group, has repeatedly posted in her official twitter account and the group's web page that IS claimed responsibility for the September 28 murder of Tavella, the October 3 killing of Japanese citizen Kunio Hoshi and Saturday's Hossaini Dalan blast.

Bur she never mentioned exactly where and how ISIS, also known as IS, made the claims.

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This is for the first time since the first claim of IS on September 28 that SITE came up with explanation where the terrorist outfit posted its claims.

The claims have been authenticated and found credible by SITE's rigorous verification process, said the press release.

"Furthermore, all of the aforementioned claims were also featured in numerous IS media channels, including Telegram Messenger and the group's publically available al-Bayan reports. Citizens and government officials in Bangladesh can even read the claims in their own language on a pro-ISIS Bengali blog," it reads.

Pointing out the Bangladesh government's "aggressively denying" of IS involvement in the attacks, SITE said: "As these misleading efforts to make ISIS' attack claims go unnoticed have failed, the government has turned its efforts toward a baseless campaign to discredit SITE, which was first to report on the claims, as well as its Director, Rita Katz."

"It would serve the Bangladesh government much better to face the truth and focus its aggression on its real enemy, ISIS, rather than on those who warn about it," reads the press release.

While reporting on IS claims immediately after Italian citizen Cesare Tavella, 50, killing in Dhaka's diplomatic zone on September 28 or Japanese Kunio Hoshi, 66, murder in Rangpur on October  3 or attack at Shia headquarters on October 24, SITE never disclosed where it got the IS claims.

As a result, media outlets around the world then had to report the claims citing SITE Intelligence Group's postings alone.