The central African country of Chad has closed its 872-mile (1,403 km) eastern border with Sudan "until further notice", Reuters news agency reports.
"Chad appeals to the regional and international community as well as to all friendly countries to prioritise a return to peace," the government said in a statement.
Gunshots could be heard in the background of a news bulletin on state-run Sudan TV.
The channel halted a news bulletin after the presenter began reading an item about the situation in Khartoum.
"We hear gunshots and explosions and we are safe here in the studio," the presenter said before the programme abruptly ended and switched to songs about unity, peace and patriotism.
Lyrics including "let us remain as one" and "the skin colour is the same, the dialect is the same" were broadcast by the network.
The fighting that has erupted in the capital, Khartoum, and elsewhere in the country is a direct result of a vicious power struggle within the country's military leadership.
Since a coup in October 2021, Sudan has been run by a council of generals - and there are two military men at the centre of the dispute.
The United Arab Emirates has called on all parties in Sudan to "exercise restraint" and "de-escalate and work towards ending this crisis through dialogue," the state news agency is reporting.
Emirates News Agency (WAM) says the Emirati embassy in Khartoum is following developments in Sudan "with great concern" and has "reaffirmed the UAE’s position on the importance of de-escalation, and working towards finding a peaceful solution to the crisis between the concerned parties".
"Furthermore, the embassy stresses the importance of efforts aimed at supporting the political process and achieving national consensus towards the formation of a government," the agency adds.
What's happening now is the latest upheaval since the toppling of Sudan's long-serving President Omar al-Bashir.
Bashir - who had been in power for nearly three decades - had been confronted by months of street protests when generals ousted him in April 2019.
The military promised a transition to civilian rule, but the demonstrators vowed to stay on the streets demanding a role in the government.
A joint military-civilian government was then agreed in August 2019, which was supposed to pave the way for elections.
But there were tensions between the sides and two years later the military staged another coup.
Since then, attempts to resurrect the plan to move towards civilian rule have hit problems.
A framework proposal agreed last December has been rejected by both pro-military and civilian groups and has not been finalised.