Arrests come as authorities suspend operations of several web-based platforms, including Facebook.

Three people have been arrested in connection with the killing of Dhaka-based blogger Niladri Chatterjee Niloy, police in Bangladesh said.

The secular blogger was murdered in early August after a gang armed with machetes broke into his house and hacked him to death, in the fourth such killing in Bangladesh since the beginning of the year.

Police said on Wednesday that “one of the suspects was held for threatening Niloy on Facebook”, while the other two were detained for “admitting responsibility” on the internet for the murder.

Related: Why are bloggers being killed in Bangladesh?

The three men, who were arrested on Tuesday, were identified as Mufti Maulana Abdul Gaffar and Islami Chhatra Shibir leaders Mortuza Sabbir Faisal and Tariqul Islam.

Shibir is the student wing of Jamaat-e-Islami, Bangladesh’s main religious party and an ally of the Bangladesh Nationalist Party in the 20-party opposition coalition.

Monirul Islam, a spokesperson from the Dhaka Metropolitan Police, told reporters that Gaffar had threatened to kill Niloy on Facebook using a profile opened under a fake name.

Faisal and Islam had opened another Facebook profile under the name of “Ansar Al Islam” and claimed responsibility for the murder, the police spokesperson added.

Web platforms suspended

The news comes as Bangladeshi authorities blocked Facebook and several other social media platforms, including WhatsApp and Messenger, on Wednesday for security reasons.

“The government has decided to suspend operation of six social networking platforms,” Sarwar Alam, secretary of Bangladesh Telecommunication Regulatory Authority, was quoted as saying by the DPA news agency.

The directives were sent out to all mobile phone operators and internet service providers, he said, adding that the operation of Facebook, Messenger, Viber, WhatsApp, Line and Tango will be suspended until further notice.

In the wake of recent attacks on secular bloggers, publishers and foreign nationals, Bangladesh’s Prime Minister Sheikh Hasina hinted earlier this month that she would order suspension of the platforms.

She said attackers might have taken advantage of the internet applications.

Foreigner attacked

In a separate incident, an Italian doctor working as a missionary was shot and injured in the neck in an attack by three assailants in northern Bangladesh on Wednesday, police said.

Piero Parolari was attacked by unidentified gunmen on a motorbike while cycling in Dinajpur, around 300km north of Dhaka, said Mir Khairul Alam, chief of the district administration.

Parolari, who was flown to Dhaka in an army helicopter for treatment, was in “serious condition”, police said.

The assault follows the killing of another Italian and a Japanese citizen at the end of September and early October.

Additional reporting by Mahmud Hossain Opu in Dhaka