In a recent article, BBC News identified for major Eurozone (highly indebted) countries, the US, the UK and Japan how much money is owed by each country to banks in other nations. Focusing on the Portuguese case, whose foreign debt amounts to 251% of GDP (equivalent to about 38.000 euros per person), the country is, first and foremost, highly indebted to Spain (65.7 bn euros). To a lesser extent it is also indebted to Germany, France and the UK (26.6bn, 19.1bn and 18.9 bn euros, respectively). Moreover, Portuguese banks are owed 7.5bn euros by Greece.
There are, naturally, worse cases starting with Ireland with a foreign debt to GDP ratio above 1000%, followed by the UK (436%), Spain (284%) and Greece (252%). Greece seems to have a figure almost identical to Portugal's level but the two countries are quite different in terms of its composition, namely the level of public debt: 100% of GDP vs. 166% of GDP for Portugal and Greece, respectively.
In the figure below (retrieved from the above-mentioned article) we can have a graphical representation of the current external debt situation in Portugal. The arrows point from the debtor to the creditor and are proportional to the money owed as of the end of June 2011 (data sources: Bank for International Settlements, IMF, World Bank, UN Population Division)