Greece saw the interest rate it has to pay to get investors to lend it money fall further Tuesday, a day after its European creditors backed the release of the country's next batch of rescue loans.

The Public Debt Management Agency said it raised 1.3 billion euros ($1.7 billion) from the sale of 13-week loans at an interest rate of 4.02 percent — that's the lowest rate since April 2011 and the second lowest in 28 equivalent auctions that started that year.

Late Monday, the finance ministers from the 16 other European Union countries that use the euro approved the release of 7.5 billion euros ($10 billion) in loans to Greece, to be paid out in May and June.

They cited "further substantial progress" in Greece's deficit-reduction program.

Weighed down by massive debts, Greece lost access to bond markets in 2010. The conservative-led government hopes to have the country return to bond markets in the first six months of 2014, as the economy emerges from a crippling recession that's sent unemployment up to a record high above 27 percent.

Also Tuesday, public servants' unions held a 24-hour strike, protesting government plans to use emergency powers and force state school teachers to call off a strike timed to coincide with annual school-leaving exams.

But Tuesday's protest failed to make any visible impact on government-run services and was criticized as a token gesture of solidarity by teaching unions which refused to join the walkout.

Public and private sector unions have also called work stoppages for Thursday, with Greece's Air Traffic Controllers' Association planning to halt flights on that day between 12:00 and 4:00 p.m. (0900-1300GMT).