New Greek PM Alexis Tsipras says his country will not default on its debts.
Addressing his first cabinet meeting since Sunday's victory, Mr Tsipras said he would negotiate with creditors over the €240bn (£179bn; $270bn) bailout.
"We won't get into a mutually destructive clash but we will not continue a policy of subjection," said the left-wing Syriza party leader.
Germany's vice-chancellor said it was unfair of Greece to expect other states to pick up its bills.
The Athens Stock Exchange fell by 8% in response to Mr Tsipras's remarks, and as it emerged that his government was putting on hold major privatisation projects, including the port of Piraeus and the main power company, the Public Power Corporation of Greece.
Greece has endured tough budget cuts in return for its 2010 bailout, negotiated with the "troika" - the EU, International Monetary Fund (IMF) and European Central Bank (ECB).
Its economy has shrunk drastically since the 2008 global financial crisis, and high unemployment has thrown many Greeks into poverty.