Kenyan President Uhuru Kenyatta on Friday dismissed salary increment of between 50 percent and 60 percent being demanded by the striking teachers, saying the present economy cannot sustain an expanded wage bill.

Speaking for the first time since over 280,000 teachers downed tools last week, Kenyatta said the current wage bill was already overstretched in relation to the economy.

"Teachers had a very legitimate case when they asked for their pay to be harmonized with the rest of the civil servants, asking for more now will mean the other civil servants will have a similar case and we will have a completely unsustainable wage bill," he added.

Kenyatta, who returned from Italy on Thursday night, said the current wage bill is already too high and such a salary increase for the striking teachers would further strain the economy.

"We have to be frank and examine our wage bill versus our present economic situation. In order to pay more, we must be able to earn more first," Kenyatta said.

The teachers have vowed not to return to class until the government meets their demands. The strike has affected close to 12 million students, 10 million in primary schools and the rest in secondary schools across the East African nation, and it is making pupils lose hope.

The impact of the two-week industrial action by teachers continues to be felt across public schools in the country, with college students and retired teachers reported to be volunteering to teach in public schools.

Organizers of the strike, Kenya National Union of Teachers (Knut) and Kenya Union of Post Primary Education Teachers (Kuppet), are however adamant that they would only head back to class after a pay increase.

The industrial action issue is already in court with the teachers' employer, Teachers Service Commission (TSC) seeking to have pay rise award reviewed.

TSC has already written warning letters to 5,000 teachers, mainly school heads, to show cause as to why they are not performing their duties.

However, the two unions have insisted that the 50 percent to 60 percent salary increment that was awarded to teachers by the Industrial Court must be effected.

A court sitting in Nairobi is set to give a ruling on the case next week. The 280,000 teachers currently account for 38 percent of Kenya's 4.2 billion U.S. dollars public wage bill.

Kenya's wage bill has been rising fast following formation of new government institutions meant to implement the requirements of the new constitution.