Italian aid worker Cesare Tavella was fatally shot three times by motorcycle-riding assailants in September. The 50-year-old man, who worked for the Netherlands-based global development agency, ICCO, was out jogging in Dhaka's Gulshan diplomatic neighborhood at the time of the attack.

Dhaka Metropolitan Police Commissioner Asaduzzaman Mia told reporters on Monday that the four arrests were made in different parts of the capital.

"All of them are wanted criminals," Mia said, adding that investigators had also recovered a motorbike believed to have been used by the perpetrators.

Government denies 'IS' responsibility claims

Three of the men were arrested on suspicion of murder, while a fourth was arrested for allegedly being the owner of the motorcycle.

Mia said the suspects claim they were hired by "a big brother" to kill Tavella to "create chaos" in Bangladesh.

"We are trying to track down the mastermind of the killing," Mia said, adding that the victim seemed to have been a random choice. Nothing was taken from the victim and police ruled out robbery as a motive.

"Islamic State" (IS) terrorists reportedly claimed responsibility for the shooting, but Bangladesh's government denied that the group has any presence in the South Asian country.

ksb/kms (AP, AFP)