(Updates blast toll, adds violence)

GUWAHATI, India, Nov 3 (Reuters) - A strike to protest against bombings that killed 84 people in India’s troubled Assam state last week shut down the region on Monday, police said, with angry Indians blaming illegal Bangladeshi migrants.

Protesters marched through the otherwise deserted streets of Guwahati, the state’s main city, where 44 people died on Thursday when three bombs exploded within minutes.

A little-known Islamist group has claimed responsibility for Thursday’s blasts in the tea- and oil-producing state, the worst strike in the troubled region, which also wounded 300 people.

Police suspect that Islamist militants working with separatists in Assam were behind the bombings.

Several students’ groups called the day-long strike across the state, demanding a crackdown on illegal settlers.

“We are going to intensify our campaign to drive out Bangladeshis from the region,” said Samujjal Bhattacharjee of the Northeast Students Organisation.

“We also appeal to people to free our society from these elements who are the real cause of terror.”

Police said they arrested 50 protesters.

The Hindu-nationalist Bharatiya Janata Party, India’s main opposition, has also criticised the government for not doing enough to stop Bangladeshi nationals from crossing over to India.

India’s home ministry says up to 20 million Bangladeshis live in India illegally.

At least 10 Muslims, mostly Bangladeshis, have been detained for suspected links with the Assam bombers, police said.

The Islamic Security Force-Indian Mujahideen sent a mobile telephone text message to a local television station claiming responsibility for the 11 apparently coordinated blasts that hit Assam within five minutes of each other last Thursday.

Police suspect the bombings were carried out to avenge attacks on Muslim settlers by indigenous tribes that killed at least 47 people in September and October.

On Monday, suspected tribal insurgents shot dead three traders in central Assam, but police could not immediately confirm whether it was retaliatory attack, saying they were investigating the killings.

They suspect illegal Bangladeshi migrants could tell them more about the involvement of Islamist groups and have detained more than 100 in a crackdown across the northeast region.

“The people were working on construction sites and they failed to provide valid documents to prove their citizenship,” a senior police officer said from Shillong, capital of neighbouring Meghalaya state.

A similar crackdown was under way in Manipur state, police said. (Writing by Bappa Majumdar; Editing by Alistair Scrutton and Paul Tait)