Some 1,500 primary and secondary schools in Serbia will go on strike Friday, while a number of others are going to cut their classes 15 minutes short and hold 30-minute lessons, all in response to the government's refusal to raise teacher salaries.

The Education Ministry has stated the strike is illegal and the participants will be punished according to the law, which includes losing their job.

The strike leaders, however, claim that the government has broken the international conventions that allow school strikes and that they are experiencing different froms of pressure, including threats, inspections and police presence.

Three unions have called for a full strike, while one called for shorter classes as a form of protest.

Education Minister Zarko Obradovic said Wednesday, after a meeting with the unions, that the government was unable to grant their demands because it would lead to higher public spending and ultimately inflation.