File Photo: Sudan s army chief and military takeover leader Abdel Fattah al-Burhan. AP
Burhan, whose October 2021 military takeover derailed a transition to civilian rule, was a senior general under Islamist-backed Bashir.
The military toppled the long-time autocrat in 2019 amid enormous street protests.
"We are warning the National Congress Party and the Islamists: do not approach the army," Burhan said in a speech to the military.
"The army does not belong to any party".
His comments come after some 3,000 protesters marched in the capital Khartoum last week, rejecting United Nations mediation efforts between civilian and military leaders as "foreign interference" and calling for a return of Islamist rule.
After Bashir's ouster, the then civilian-led authorities passed a law in 2019 ordering the NCP be dissolved, its assets seized and the regime dismantled.
But after last year's military takeover, civilian leaders were arrested, and the military authorities have since returned property to certain NCP ex-leaders, while some Islamist figures have regained positions of power.
The NCP said in a statement later Sunday: "Burhan, you know very well that the armed forces are loyal to the organisation", referring to Bashir's Islamist regime.
"We will not let you hand over the country to mercenaries and embassy collaborators again," it added.
Sudan has been mired in a political and economic crisis since last year's military takeover. Security forces have cracked down on near-weekly protests, resulting in at least 119 deaths, according to pro-democracy medics.
Civilian leaders have refused to negotiate with the military before it commits to a timetable for full withdrawal from power.
The only proposal so far considered by both civilian leaders and the military is a transitional constitution developed by the Sudanese Bar Association, which would impose a ban on NCP activity.
Bashir, 78, has been in custody in Khartoum since his 2019 ouster.
He has been convicted of corruption and has also been on trial over the Islamist-backed 1989 coup which brought him to power.
Bashir has been wanted by the International Criminal Court for more than a decade over charges of genocide, war crimes and crimes against humanity in Sudan's western Darfur region.