Amid mounting pressure from ally Dravida Munnetra Kazhagam and other Tamil Nadu parties, Prime Minister Manmohan Singh [Images] on Saturday asked Sri Lankan President Mahinda Rajapaksa to ensure that Tamils do not get 'enmeshed' in the conflict with LTTE [Images] and that their rights and safety are upheld.

During a telephonic conversation initiated by Rajapaksa, Dr Singh said there could be no military solution to the conflict in the island country and asked the President to start a political process for a peacefully negotiated settlement within the framework of a united Sri Lanka [Images], the Prime Minister's Office said.

The prime minister also asked Rajapaksa to instruct the Sri Lankan Navy to desist from firing on Indian fishermen, saying their killing is 'unacceptable', the PMO said in a statement.

Rajapaksa assured Dr Singh that 'all necessary measures' are being taken to ensure safety and well-being of the Tamil community in Sri Lanka, it said.

'During the telephonic conversation, the Prime Minister expressed his deep concern on the deteriorating humanitarian situation in the north of Sri Lanka, especially on the plight of civilians caught in the hostilities,' the statement said.

Dr Singh emphasised that the 'safety and the security of these civilians must be safeguarded at all costs'.

Dr Singh told Rajapakse that 'rights and welfare of the Tamil community of Sri Lanka should not get enmeshed in the ongoing hostilities against the LTTE', the PMO said.

During the conversation, the prime minister said continued and uninterrupted relief supplies should be ensured for the internally displaced persons in order to address the humanitarian situation, the PMO said.

On the killing of Indian fishermen, Dr Singh and Rajapaksa agreed to work on practical arrangements to prevent such incidents.

The conversation came amid a spree of resignations by DMK members in the Union Cabinet and MPs to their party chief to protest against the military offensive in LTTE-held areas in Sri Lanka.

The prime minister had on Wednesday said the situation in the island nation is a cause for 'serious concern' and asked Colombo to find a negotiated settlement rather than looking for a 'military victory'.

He said India was concerned over escalating hostilities, losses suffered by civilians and increasing number of displaced persons in Sri Lanka.

Foreign Secretary Shivshankar Menon on Friday summoned Lankan High Commissioner C R Jayasinghe and told him that Colombo should address New Delhi's [Images] concerns over the humanitarian situation in the island nation and stop harassing and killing Indian fishermen.

Menon said Sri Lankan government should ensure that the rights of its civilians are respected and they are protected from attacks.