The doctor, who is being held under emergency laws, is still behind bars. (Representational)

A Muslim doctor falsely accused of secretly sterilising Buddhist women in Sri Lanka remains in detention weeks after his arrest, despite investigators saying he was framed.

Mohamed Shafi was arrested on May 24 over claims he had carried out the illegal sterilisations of thousands of Sinhalese women.

But court documents seen by AFP show investigators are adamant he was set up.

Communal tensions in Sri Lanka are at boiling point since the Easter Sunday (April 21) suicide bombings by Islamist militants of churches and hotels, which left 258 dead and hundreds wounded.

Pressure has since mounted on Sri Lanka's Muslims, who make up about 10 percent of the island's 21 million population.

Shafi was detained after a Sinhalese-language daily published unsourced allegations that he had sterilised 4,000 women from the Buddhist-majority population.

It also tied him to membership of the Islamic group blamed for the Easter bombings.

Other media leapt on the claims, accusing Shafi of performing 8,000 caesarian section surgeries and surreptitiously carrying out sterilisations only on Sinhala Buddhist women.

But the Criminal Investigations Department (CID) told a court it had found no evidence to support the allegations against Shafi, explaining his colleagues said other medical staff would have noticed the procedures.

"There is no justification for the arrest of Dr. Shafi," the CID concluded in a 210-page report.

The CID told the court that Deputy Inspector General of Police Kithsiri Jayalath, chief in Shafi's home region of Kurunegala, fabricated evidence and fed the allegations to the Sinhalese newspaper.

But Shafi, who is being held under emergency laws, is still behind bars, prompting calls for his release.

Some hardline Buddhist monks have waded into the issue, demanding for the "stoning to death" of the renowned surgeon.

Sri Lankan Muslim leaders say the Easter attacks have taken simmering communal tensions to a new level, with mosques searched in a police dragnet for the terror cell.

A campaign of "hate" was now in full swing, lawmaker and Sri Lanka Muslim Congress leader Rauff Hakeem told AFP.

"There had been a build-up of a narrative (against Muslims) for more than a century in this country, based on business rivalry, jealousy."

As Shafi is being held under the emergency law, he can only be freed by the defence secretary and a legal struggle is underway to release him.

Muslim leaders have urged their community to also look within for ways to defang the communal tensions.

Muslim women covering their face was a new phenomenon in Sri Lanka that had deepened suspicions among other communities, Hakeem said.

Islamic clerics have endorsed government moves to ban full face covering, including the niqab, for women.