Lagos - Nigerian President Goodluck Jonathan said on Monday he had ordered a probe into a rash of allegations, including the creation of a political hit squad, levelled against him by former leader Olusegun Obasanjo.
Obasanjo, who served as president from 1999-2007, penned an open letter to Jonathan on 2 December that accused him of training a private militia to assassinate political rivals.
A founding member of Jonathan's Peoples Democratic Party (PDP), Obasanjo also accused the president of gross incompetence and urged him not to seek reelection in 2015.
Obasanjo's letter has dominated headlines in Africa's most populous country this month and Jonathan said he was compelled to publicly reply because the missive posed "a threat to national security".
"Perhaps the most invidious accusation in your letter is the allegation that I have placed over one thousand Nigerians on a political watch list, and that I am training snipers and other militia to assassinate people," Jonathan said in the reply.
Jonathan dismissed the charge as "baseless" and "incomprehensible" and demanded Obasanjo offer proof.
But, he added that he has "nevertheless... directed the security agencies and requested the National Human Rights Commission to carry out a thorough investigation of these criminal allegations and make their findings public".
While Nigeria has been gripped by the bitter public feud between the two political titans and onetime allies, the spat has mounted further pressure on Jonathan to declare his plans for the 2015 polls.
The president has been hemorrhaging support in recent weeks, including the defection from the PDP of five powerful state governors to the opposition All Progressives Congress (APC) last month.
The PDP, which has controlled all branches of the federal government since the end of military rule in 1999, also lost its majority in parliament last week after 37 lawmakers defected to the APC.
Obasanjo hosted senior APC leaders at his home on Saturday.
In weighing a re-election bid, Jonathan has been accused of breaking an unwritten PDP rule that calls for the presidency to rotate between southern Christians, like Jonathan, and northern Muslims.
The country's 170 million people are roughly split between the two faiths.
"I will only speak on whether or not I will seek a second term when it is time for such declarations," Jonathan's letter said.