The DMK ministers led by TR Baalu on Tuesday night met President Pranab Mukherjee and handed over the letter to withdraw support from the UPA government. The DMK ministers will also meet Prime Minister Manmohan Singh on Wednesday.
Earlier in the day, DMK chief M Karunanidhi announced that his party was leaving both the multi-party coalition and Prime Minister Manmohan Singh's government after New Delhi's failure to take a hard line against Sri Lanka.
"Continuing in this government will be an injustice to the Sri Lankan Tamils," the former Tamil Nadu chief minister said in Chennai, and charged Colombo with committing atrocities on its Tamil population.
The 88-year-old politician accused both India and the UN of "betraying" the Sri Lankan Tamils.
But Karunanidhi made it clear that if the government accepted his two demands - charge Sri Lanka with "genocide" of Tamils and demand a credible investigation into alleged war crimes -- he could reverse his stand.
Karunanidhi said the UPA government had not only refused to consider the DMK's views on the US-sponsored resolution against Sri Lanka at the UNHRC session in Geneva but had quietly watered it down.
He ruled out extending outside legislative support to the UPA, in which the DMK was the largest constituent after the Congress.
As the DMK decided to withdraw support, the government on Tuesday moved to bring a resolution on the Sri Lankan Tamil issue in Parliament in an attempt to placate the key ally which has set it as one of the conditions for reconsideration of its decision.
Sources said the government is drafting a resolution to be brought in Parliament.
The decision was taken after the Congress Core Group meeting, hours after DMK chief M Karunanidhi announced that his party would withdraw support to the UPA.
However, the DMK has made it clear that it would reconsider its decision if India supports a strong resolution at the UN Human Rights Council and brings a resolution in Parliament on the issue.
Earlier, finance minister P Chidambaram insisted that the government faces no threat and that consultations have been initiated with political parties on DMK's demand that Parliament should adopt a resolution on human rights violations in Sri Lanka.
Chidambaram said the Congress Core Group, headed by party chief Sonia Gandhi, had considered the two suggestions made by DMK at length.
He sought to mollify Karunanidhi, saying his "statement deserves all respect".
Asked whether he was hopeful that DMK will reconsider its decision, Chidambaram said, "According to the media, the DMK president has said that he will review its decision if a resolution is brought before Parliament. We take note of that statement also."
He insisted that the government is stable and will continue.
Read more: DMK pulls out of UPA govt, 5 ministers to resign
"Let me assure everyone that the stability of the government and the continuation of the government are not an issue. The government is absolutely stable and enjoys majority in the Lok Sabha," he said.
"The government has a majority in the House," Chidambaram said responding to repeated queries on the issue of the government's stability.
His statement came hours after Karunanidhi announced that the DMK will pull out of the government over the Lanka Tamils issue. The DMK has 18 members in the Lok Sabha and the UPA with the support of the DMK has 303 MPs in the 543-member House.
Read more: The other foreign hand
On the issue of a resolution moved at the UNHCR against Sri Lanka which DMK wants India to support, he said that the government is examining the final draft which reached here late last night.
Sonia pitches for credible probe
Congress president Sonia Gandhi on Tuesday backed the southern ally's demand for an independent and credible probe into "unspeakable atrocities" on ethnic Tamils in Sri Lanka, saying these cannot go un-investigated.
She said that the Sri Lankan Tamils continue to be denied legitimate political rights and expressed pain and anguish over this state of affairs.
Read more: No threat to govt's stability: Chidambaram
Her remarks while addressing a meeting of the Congress Parliamentary Party came a day after DMK supremo M Karunanidhi made a strong pitch for establishment of a credible and independent international commission of investigation in a time bound manner into allegations of war crimes against Tamils in Sri Lanka.
Union ministers AK Antony, Ghulam Nabi Azad and P Chidambaram at DMK chief M Karunanidhi's residence in Chennai. PTI
As senior central ministers explored ways to placate the DMK, Gandhi said, "The plight of Tamils in Sri Lanka is close to our hearts. Our support for equal rights and equal protection of the laws to them has been unwavering since the days of Indiraji and Rajivji.
"We are most pained at the manner in which their legitimate political rights continue to be denied to them. We are anguished by reports of unspeakable atrocities on innocent civilians and children, especially during the last days of the conflict in 2009," she said.
She also noted that the plight of Indian fishermen, who are being detained or fired upon by the Sri Lankan navy is a matter of great concern. "A permanent solution to the daily violence against them is also imperative," Gandhi said.
Read more: DMK might just reconsider pull-out, says NCP
Karunanidhi had warned that he would withdraw unless the government supported a resolution at the United Nations Human Rights Council in Geneva that condemned "genocide and war crimes" in Sri Lanka.
Sri Lankan forces ended a decades-long civil war with a 2009 onslaught against Tamil Tiger separatists which has since been dogged by war crimes allegations.
The UN estimated that some 40,000 people were killed in the final months of the war, while rights groups put the death toll even higher. Sri Lanka denies that its forces killed civilians.
Chidambaram, who along with defence minister AK Antony and health minister Ghulam Nabi Azad, had met Karunanidhi on Monday, said the government is also examining whether amendments can be moved to that draft to strengthen that resolution as demanded by DMK.
"As far as the resolution in the UNHCR is concerned, we are examining the final draft that came to us late last night and whether amendments can be moved to that draft to strengthen that resolution," he said.
(With inputs from PTI, AFP)