ISIL claimed responsibility for shooting a Japanese man in Bangladesh on Saturday, the second foreign national it says it has killed in the Muslim-majority country within a week.
Police said they had detained four suspects in connection with the shooting of Kunio Hoshi, 65, in Rangpur district, 210 miles north of the capital, Dhaka, in an attack similar to the shooting on Tuesday of Italian Cesare Tavella.
"This (Hoshi's) killing was also carried out by three masked men who came by motorcycle and used a pistol, so the motives may be same," Home Minister Asaduzzaman Khan told Reuters, before the claim of responsibility.
Attacks on foreigners are rare in Bangladesh. But it has seen a rising tide of sectarian violence over the past year, in which four secular bloggers were hacked to death, among them a U.S. citizen of Bangladeshi origin.
On Saturday, the Islamic State of Iraq and the Levant (ISIL) warned of more attacks.
"There will continue to be a series of ongoing security operations against nationals of crusader coalition countries, they will not have safety or a livelihood in Muslim lands," the group tweeted.
U.S. Ambassador to Bangladesh Marcia Bernicat said in a statement that she was saddened by the latest killing.
"I urge the government of Bangladesh to investigate every aspect of this crime and to bring the perpetrators to justice as soon as possible," she said.
One of the four detained people was a rickshaw puller and another was the owner of a residence near where the attack took place, police said.
Security will be increased at foreign diplomats' and foreign nationals' homes and workplaces, a high level meeting decided on Saturday, Inspector General of Police AKM Shahidul Hoque said.