Layoffs cascaded through the federal government on Thursday after its human resources division advised agencies to terminate most of an estimated 200,000 workers on probation, a sharp escalation in the Trump administration’s drive to overhaul and shrink the federal work force.

Among the largest layoffs reported on Thursday was one announced by the Department of Veterans Affairs, which dismissed more than 1,000 employees, including probationary workers who had worked at the agency for less than two years. Employees at several other agencies also reported receiving termination notices, though the full extent of the cuts in many departments was not immediately clear.

Regardless, the layoffs could mark a major increase in the scale of the Trump administration’s efforts to shed federal workers and reshape government. The administration had already said that about 75,000 workers had accepted an offer to resign in exchange for being paid through September, but the removal of most workers on probation, generally recent hires who have been in their roles less than a year, could cut much deeper into the federal government’s civilian work force of 2.3 million.

The cuts even extended to the agency ordering them, the Office of Personnel Management, which manages the federal civilian work force. It laid off dozens of employees on Thursday, according to people familiar with the move.

The dismissals came on the same day that leaders at O.P.M. met with agency representatives and urged them to lay off most probationary employees, according to a person familiar with the matter who was not authorized to speak about the issue publicly.

Many employees on fixed-term assignments at the Consumer Financial Protection Bureau were also terminated on Thursday, according to several people familiar with the matter. The dismissals came after more than 70 probationary workers at the bureau were laid off earlier this week.