DHAKA - At least six people were injured, with three in a critical condition, after a series of bomb blasts on Saturday at a Hindu religious gathering in northern Bangladesh, a police official said.

The attack follows the shooting and wounding of an Italian doctor working in the same region last month, and the earlier murders of an Italian and a Japanese citizen in separate attacks claimed by Islamic State.

The latest incident occurred in Dinajpur district, 415 km (260 miles) north of the capital Dhaka when a series of bombs exploded as hundreds of devotees attended a religious ceremony known as “Rushmela”, Abdul Mazid, the officer in-charge of Kahalur police station, told Reuters.

The attack came after recent threats to the temple’s priest, urging him not to organise any religious gatherings, Mazid said. Five people had been detained for interrogation, he said. Bomb attacks on Hindu religious gatherings are rare in Muslim-majority Bangladesh.

The country has suffered a rising tide of Islamist violence over the past year. Four online critics of religious militancy have been hacked to death, among them a U.S. citizen of Bangladesh origin. Moreover, Security forces in Bangladesh arrested six people on Friday on suspicion of human trafficking and currency smuggling and possible involvement in militant activity, a spokesman for the special forces Rapid Action Battalion said.

One Pakistani national was among the men detained at different locations in the capital Dhaka, Mufti Mahmud Khan told Reuters. Some 10 million counterfeit Indian rupees and 624,000 Bangladeshi taka ($8,000) were also found, along with large amounts of foreign currency including U.S. dollars, Pakistani rupees, UAE dirhams and Saudi riyals.

“We are investigating whether they were mobilising funds for militant activities in Bangladesh and or planning to carry out destructive action in the country,” said Khan. “We will be able to confirm only after completion of interrogation.”

Authorities also found 21 passports and a large number of fake document stamps, he said. In a separate case, the detective and criminal intelligence division of the Bangladesh police (DCIDB) arrested three Pakistani nationals and one Bihari man from Bangladesh on Monday on suspicion of involvement in militant activity.

Biharis are among the Urdu-speaking groups known as “stranded Pakistanis” who settled in what is now Bangladesh after India was partitioned. DCIDB spokesman Muntashirul Islam told Reuters that the men were members of a banned group, Jama’atul Mujahideen Bangladesh (JMB), and had planned to sabotage key installations and carry out targeted killings aimed at destabilizing the government.

“They were arrested on charges of spying, conspiracy to commit murder and acts of terror and other crimes,” he said. Police named the suspects as Idris Sheikh, Mokbul Sharif, Mohammad Salam and Mohammad Mostafa and said they had recovered five mobile phones, 26 jihadist books, three Bangladeshi passports, 4,000 Pakistani rupees and other currencies.