* Troika due to visit next week
* Plans to overhaul and reduce state sector
* Fierce resistance from trade unions (Adds quotes, troika visit, minister quote)
By Deborah Kyvrikosaios and Renee Maltezou
ATHENS, Sept 16 (Reuters) - Greek police fired teargas to disperse dozens of school guards who tried to force entry to the country's reforms ministry on Monday, as public sector workers began a week of strikes to protest planned layoffs demanded by foreign creditors.
After a summer lull, guards, who patrol school premises and oversee road crossings, teachers and public hospital doctors are starting walk-outs to put pressure on the government ahead of an inspection next week by the "troika" of European Union and International Monetary Fund officials.
"We want our jobs back!," Eleni Stathaki, a 53-year-old former school guard, said in tears. "They threw us out but want us to keep paying taxes. It's impossible to live like this."
Stathaki was among 300 protesting guards, rallying outside the Administrative Reform Ministry as ministers discussed the measures early in the morning.
Later, thousands of protesting state workers marched through the streets of Athens to parliament chanting "Let's kick the government, the EU and the IMF out!" and holding banners reading "No firings!"
Firing workers is a sensitive issue in the crisis-hit country, where unemployment has hit nearly 28 percent and poverty levels have soared during a six-year recession.
Reforming a state apparatus widely seen as corrupt and bloated, where hirings were often made for political patronage, is a key demand from creditors to ensure continued bailout funding for the country.
Education Minister Konstantinos Arvanitopoulos said reform in the sector would save taxpayers millions of euros.
"We need to move forward with all the structural reforms that will make our educational system better and less wasteful," Arvanitopoulos told Reuters.
Athens must put thousands of state workers in a so-called mobility scheme by the end of the month, where they will be evaluated and transferred to other jobs or dismissed, as part of a plan to shrink and overhaul its state sector.
But the scheme has met fierce resistance from labour unions.
Only a few days after the school year began, high-school teachers started an open-ended strike saying firings or transfers will add to the pain felt by austerity-hit households. Elementary school teachers and university professors intend to join them with separate walkouts and work stoppages this week.
Workers at Greece's largest social security fund, the IKA, also walked off the job on Monday. State hospital doctors will start a three-day strike on Tuesday.
They are all expected to join a 48-hour strike on Sept. 18-19 called by Greece's largest public sector union ADEDY, which represents about half a million state workers.
Greece must place a total 25,000 workers in the mobility scheme by the end of the year and must also meet a target of 15,000 mandatory public sector exits in 2013-14.
Since 2009, it has cut the state workforce by 22 percent to 680,000 jobs mainly through attrition rather than layoffs. (Additional reporting by George Georgiopoulos; Editing by Ralph Boulton)