ATHENS, Greece (AP) — Hundreds of striking Greek civil servants, mostly school teachers, are marching through central Athens to protest proposed new hiring criteria for state school teachers.

The left-wing Greek government has promised to hire 15,000 full-time teachers over the next three years, starting this fall.

But unions say the hiring system is unfairly weighted against teachers who have been working for years on short-time contracts. They also want more teachers to be hired.

The umbrella civil servants' union, Adedy, has called a 24-hour public sector strike Thursday to back the teachers' demands, although the walkout mainly affected schools.

Teachers have held two protest marches in Athens over the past week over the hiring plan that were both marred by clashes between some demonstrators and riot police.