Heavy gunfire disrupted a 24-hour truce pact in Sudan on Tuesday, just before it was set to go into effect, as the United States pressed competing military factions to halt fighting that has triggered a humanitarian disaster.

Loud shooting echoed in the distance of live feeds by Arab news television networks in the Khartoum metropolitan region minutes after the ceasefire agreement's agreed-upon start time of 6 p.m. (1600 GMT).

PHOTO | COURTESY Sudan clashes

Warplanes roared above Khartoum, and witnesses claimed a massive military ground force entering the city from the eastern side.

According to United Nations spokesman Stephane Dujarric, there has been no ceasefire in the fighting.

Sudan's army leader and deputy on the ruling council clashed four days ago, derailing an internationally supported plan for a civilian democratic transition four years after Islamist autocrat Omar al-Bashir was removed from power by a popular Arab spring uprising and two years after a military coup.

The war has resulted in what the UN has termed a humanitarian disaster, including the near-collapse of the health system. Across the vast country, at least 185 people have been killed.

Speaking in Japan, US Secretary of State Antony Blinken said on Tuesday the United States had phoned both army chief General Abdel Fattah al-Burhan and Rapid Support Forces (RSF) paramilitary leader General Mohamed Hamdan Dagalo, appealing with their rival forces to cease fire "to enable the Sudanese to be safely reunited with families" as well as offering them with aid.

PHOTO | COURTESY Sudan clashes

According to Army General Shams El Din Kabbashi, a member of Sudan's ruling army council, who appeared earlier on al Arabiya TV, the ceasefire agreement would only be extended within the agreed-upon 24-hour timeframe.

Amid the chaos, it was unclear who was behind the different bursts of gunfire. The RSF posted a Facebook statement shortly before the truce's implementation, blaming the army for violations.

According to one local, an air strike was carried out in Omdurman, Khartoum's sister city on the opposite bank of the Nile River.

Fighting seemed to have subsided as the truce deadline approached, coinciding with the nighttime break of the daily fast during Ramadan.

The death toll in the recent clashes has crossed the 200 mark, and thousands of others are injured. The death toll is expected to rise as the fighting continues.