Nurses, teachers, prison guards, firefighters and judges have staged walkouts and street protests in recent weeks and days, demanding better salaries and contract terms.
"The country is experiencing growth in income and employment," Centeno, who also leads the Eurogroup of euro zone finance ministers, told a parliamentary committee.
"These are the moments when people become more demanding," he said, describing this as an "absolutely normal" response.
There have been a total of 173 public sector strikes so far this year, compared to 87 in 2015, the year the Socialist government came to power, according to calculations by the Jornal de Negocios newspaper.
The previous central-right administration's austerity drive following Portugal's 2011-14 bailout had caused widespread strife, although it was at a lower level than in Greece or Spain which also faced a period of economic turmoil.
The Socialists and their left-wing allies have reversed some austerity measures while maintaining budget discipline to reduce the deficit. The economy last year grew at its strongest pace since 2000. Growth slowed slightly this year but unemployment dropped to 16-year lows.
Earlier this month, the government increased the minimum public sector monthly wage to 635 euros a month from 580 euros.
(Reporting by Gonçalo Almeida and Catarina Demony Editing by Andrei Khalip and Edmund Blair)
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