Court premises in the Zambian capital, Lusaka, and elsewhere have been shut as the deadline for filing a petition against the outcome of the recent presidential election approaches.
An unusual police presence has been reported at some courts, which have been taped off to prevent access.
Opposition candidate Brian Mundubile said he would challenge the election result, citing irregularities, after coming second with a 38% share of the vote. Incumbent Hakainde Hichilema won a second term with 60%.
Mundubile is in hiding over alleged threats made against him, amid a post-election period marked by controversy, including the shooting dead of an opposition figure and the arrest of others.
Monday is the last day on which petition against the presidential election result can be filed. Such a petition could potentially affect the inauguration of Hichilema, which is scheduled for 1 September.
On Monday, lawyers who arrived at the courts were being asked to depart.
One lawyer told the BBC that three-armed men approached his vehicle, identified themselves, and instructed him to leave the area.
The courts that have been sealed off include the High Court in Lusaka, the Supreme Court, which also houses the Constitutional Court, and several local courts.