Bangladeshi police officials stand guard at the site where a Japanese citizen was shot to death by attackers on Saturday. (Stringer/AFP/Getty Images)

The Islamic State claimed responsibility for shooting a Japanese man in Bangladesh on Saturday morning, the second foreign national it says it has killed here within a week, and the group threatened more such attacks.

The incident took place at Mahiganj village in Rangpur district, said Rezaul Karim, a police official.

The victim was identified as Kunio Hoshi, around 50, Karim said, adding that Hoshi had started a farm in Rangpur, about 185 miles north of the capital, Dhaka, to produce grass.

Local residents said two bike-riding assailants fired at Hoshi three times on Saturday, Karim said. Police have detained four people for questioning, he said.

Saturday’s killing occurred five days after an Italian aid worker was killed by motorbike-riding assailants in Dhaka. The Islamic State also claimed responsibility for that attack.

Bangladeshi police officials stand guard at the site where a Japanese citizen was shot to death by attackers in Rangpur Saturday. (Stringer/AFP/Getty Images)

The government, however, dismissed the claim, saying that there was no evidence. It described the killing as an “isolated incident.”

The aid worker, Cesare Tavella, had been working in Dhaka for a Netherlands-based church cooperative, serving as program manager for a project focusing on food security and economic development for people living in rural areas in Bangladesh.

The Islamic State 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 posted Saturday on Twitter.

Attacks on foreigners are rare in Bangladesh. But there has been a rising tide of Islamist violence over the past year in which four online critics of religious militancy were hacked to death.

Among them was a U.S. citizen of Bangladeshi origin.

The Japanese and South Korean embassies, along with those of Western countries, have all issued warnings for diplomats and citizens to be extra vigilant about their personal security.

Marcia Bernicat, U.S. ambassador to Bangladesh, 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.

At a high-level meeting on Saturday, it was decided that security will be increased at foreign diplomats’ and foreign nationals’ homes and workplaces, Inspector General of Police A.K.M. Shahidul Hoque said.