Statement comes a day after announcement of top mullah's death, though it is unconfirmed

The Afghan Taliban, who have been fighting to topple the Kabul government for almost 14 years, said on Thursday that they were "not aware" of a new round of peace talks due the following day in Pakistan in a statement indicating the group may be pulling out of the negotiations.

The apparent rejection of the talks comes a day after Kabul announced the death of the Taliban's reclusive leader Mullah Mohammad Omar, but it was not immediately clear if the two developments were connected.

The Afghan intelligence service asserted on Wednesday that Mullah Omar died in a Karachi hospital more than two years ago. In Washington, the US government said it considered the report of the Taliban leader's death credible, though it was not confirmed by the Taliban or Pakistan.

Afghan President Ashraf Ghani's office said Mullah Omar's death would strengthen conditions for the peace process, which has been his priority since he took office last year.

The first round of the official, face-to-face discussions was hosted by Islamabad earlier this month. The meeting was supervised by US and Chinese representatives and ended with both sides agreeing to meet again - a significant progress in itself.

This week, Afghan and Pakistani officials said the second round would take place on Friday, in the Pakistani resort town of Murree. But Thursday's statement from the Taliban, who call themselves the "Islamic Emirate", contradicted that.

"The Islamic Emirate has handed all agency powers in this regard to its Political Office and they are not aware of any such process," the statement said, referring to the talks.

The statement made no mention of Mullah Omar or his reported death. The Afghan government has not presented any evidence to back up its claim that the Taliban leader is dead and Kabul did not have an immediate comment on the Taliban statement. Ghani's office said he had flown to Germany on Wednesday for minor medical treatment.

The Taliban have been fighting to overthrow the Afghan government since 2001, when the United States led an invasion to topple its extremist rule.

The allegedly enduring leadership of Mullah Omar, despite numerous past reports of his death, had provided a unifying force for fighters on the ground and for those on both sides who have pushed the peace process forward in the months since Ghani took office.

If confirmed, his removal creates a leadership vacuum in the Taliban, and appears to have exposed rifts at the top of the organization, which is widely believed to be split among those who support and reject contact with Ghani's government.

Political analyst Ahmad Saeedi said the Taliban's statement could signal a total rejection of the peace process by the movement. "I'm pretty sure there will be no peace deal," he said.

Observers see a further fracturing within Taliban ranks likely to lead to a power struggle. Already, the Islamic State group, which has taken control of large parts of Iraq and Syria, is believed to have recruited some disaffected Taliban members to its ranks as it tries to establish a presence in Afghanistan.

For his part, Ghani has sought Pakistan's help in bringing the Taliban to the negotiations, since Islamabad is believed to wield influence over the group.

A diplomat based in Kabul familiar with the peace process said that the "government's position has been since Ashraf Ghani became president that the real negotiation is between Afghanistan and Pakistan".