By Saroj Pathirana
BBC Sinhala service
Mr Saravanamuttu has been the target of death threats
A panel of international lawyers says it is alarmed over reports that human rights activists and reporters are being intimidated in Sri Lanka.
The International Bar Association's Human Rights Institute also voiced concern that criminal charges could be brought against activists by Colombo.
It says that 35 activists critical of the government had been listed according "to their level of dissent".
Sri Lanka maintains there is no intimidation against rights activists.
International Bar Association's Human Rights Institute (IBAHRI) describes itself as the global voice of the legal profession.
It says that prominent Sri Lankan human rights lawyer JC Weliamuna and rights activist Paikiasothy Saravanamuttu are "understood to have been placed at the top of a list", to be targeted by the authorities.
IBAHRI says 35 activists, lawyers and journalists who have been critical of the government have been listed.
The government has not officially commented on the alleged list.
IBAHRI says it is "deeply concerned" for the safety of Mr Weliamuna and Mr Saravanamuttu "who have previously been subject to serious coercion, including physical attacks and death threats".
Amnesty International, Human Rights Watch, Transparency International Sri Lanka (of which Mr Weliamuna is the executive director), the Centre for Policy Alternatives (headed by Dr Saravanamuttu) and the Asian Human Rights Commission have also urged the Sri Lanka authorities to end their "witch hunt".
In recent weeks, Sri Lankan Prime Minister Ratnasiri Wickremanayake and ministers have warned that international and domestic groups found to be "conspiring against the government" will be banned.
A recent report by the US state department has raised concern over threats against human rights activists in Sri Lanka.
Alex Wilks of IBAHRI told the BBC Sinhala service that it had been approached by international organisations expressing concern.
"We are worried that these criminal charges are being brought against Mr Weliamuna with a view to intimidating him and preventing further activities," Mr Wilks said.
Juan Mendez, IBAHRI co-chairman, urged the Sri Lankan government to demonstrate its commitment to democratic principles "by ensuring that freedom of expression and accountability are made a reality for all its citizens".