Sri Lanka has held its first mass funeral amid a day of mourning for the victims of Sunday’s bomb blasts.

The death toll from the attacks on churches and hotels has risen to 321 with about 500 wounded, police said.

A state of emergency is in effect to prevent further attacks.

The Islamic State (IS) group claimed the attack on Tuesday via its news outlet. Sri Lanka’s government has blamed the blasts on local Islamist group National Thowheed Jamath (NTJ).

The country’s prime minister, Ranil Wickremesinghe, said the government believed there “may be links” to IS. “This could not have been done just locally,” he said. “There had been training given and a coordination which we are not seeing earlier.”

The IS statement should be treated cautiously. As with previous attacks that the group says it carried out, it has provided no evidence for the claim.

Police have now detained 40 suspects in connection with the attack. A spokesman said they included a Syrian who was arrested “after the interrogation of local suspects”.

The mass funeral for about 30 victims took place at St Sebastian’s church in Negombo, north of Colombo, which was one of the places targeted in Sunday’s blasts. Another funeral service was scheduled for later on Tuesday.

Earlier, a moment of silence was observed at 08:30, reflecting the time the first of six bombs detonated. Flags were lowered to half-mast and people, many of them in tears, bowed their heads in respect. The state of emergency gives police and the military sweeping powers to detain and interrogate suspects without court orders – powers that were last used during the nation’s civil war.

The government limited access to Facebook, WhatsApp and Instagram after the blasts.

NTJ, the group named by the government as the main suspect, has no history of large-scale attacks but came to prominence last year when it was blamed for damaging Buddhist statues. The group has not said it carried out Sunday’s bombings. The state of emergency gives police and the military sweeping powers to detain and interrogate suspects without court orders – powers that were last used during the nation’s civil war.

Cabinet spokesman Rajitha Senaratne said the information was not passed to Mr Wickremesinghe due to a rift between the prime minister and President Maithripala Sirisena. However, it was not clear on Monday whether Mr Sirisena had been made aware of the warnings.

“Our understanding is that it was correctly circulated among security and police,” Shiral Lakthilaka, a senior adviser to Mr Sirisena, told the BBC. He said that the president had appointed a special committee led by a supreme court judge to investigate what had happened.