DHAKA:  Bangladesh arrested four suspects who allegedly said they were hired to carry out last month's killing of an Italian citizen in the Bangladeshi capital in order to create instability in the impoverished South Asian nation, police said Monday.

Italian aid worker Cesare Tavella was gunned down by motorcycle-riding assailants while jogging on the streets of the Dhaka's diplomatic quarter. Five days later, a Japanese citizen was killed in a similar attack in northern Bangladesh.

The killings spooked the country's expatriate community and threatened to its fragile economy, which is heavily reliant on foreign aid and a $25 billion garment industry supplying clothing for international brands.

Responsibility for the attack on Tavella was quickly claimed by the Islamic State group, but the Bangladeshi government denied the extremist Sunni militant group had any presence in the country. Instead, Bangladesh accused domestic Islamist militants and Islamist politicians of orchestrating the violence to destabilize the already fractious nation.

On Monday, Dhaka Metropolitan Police Commissioner Asaduzzaman Mia told reporters on Monday that authorities had arrested three men suspected of carrying out the killing, as well as the owner of a motorcycle suspected of being used in the attack. They are still hunting for the alleged mastermind.

Mia said the suspects were known professional killers and were identified from closed circuit footage from the attack site.

They told investigators they were hired by "a big brother" to kill Tavella to "create chaos" in the country, Mia said. "We have identified that so-called big brother. When we are able to arrest that man, it will be clear who used them."

The attackers allegedly targeted Tavella simply because he was Caucasian, and that the suspects were promised payment for the attack. "Tavella was not their specific target, he just became a victim being a white," Mia said.