The RSF sent 52 vehicles in addition to the troops already deployed in the city, Al Arabiya said.
Reinforcements also arrived to support RSF troops deployed in the capital city of Khartoum, according to Sudanese social media.
In the early hours of Thursday, the Sudanese army released a statement, saying that the RSF began moving into Merowe in what was a "clear violation of law" done without prior coordination or notification. The RSF, in turn, claimed their operations in Merowe were part of their duties.
The Sudanese army had also deployed its troops in Merowe in the event of a further escalation, giving the RSF time to vacate the city, Al Arabiya reported earlier in the day, citing its sources.
On Wednesday, Merowe officials reported about the deployment of about 100 military vehicles belonging to the RSF in the city.
Several Sudanese politicians as well as international mediators engaged in the settlement of the conflict called for restraint and peaceful negotiations.
The Forces of Freedom and Change, the Sudanese opposition coalition, said on April 6 that the signing of a final political agreement, which would provide for the establishment of a transitional civil authority in Sudan, had been again postponed due to lack of consensus between the two opposing parties.
Gen. Abdel Fattah Burhan, chairman of the Transitional Sovereignty Council and commander-in-chief of the Sudanese military, and Gen. Mohamed Hamdan Dagalo, his deputy and commander of the RSF, could not agree on the process of integration of RSF into the regular army.