German Chancellor Angela Merkel
German Chancellor Angela Merkel has arrived amid heavy security for her first Greek visit since the eurozone crisis erupted nearly three years ago.
Some 7,000 police officers are on duty, with protests banned in certain areas.
However, many people who blame Germany for forcing painful austerity measures on Greece streamed into central squares carrying anti-Merkel banners.
Correspondents say this highly symbolic visit is a show support for Greece's continued membership of the eurozone.
It comes as Greece prepares to pass new cuts of 13bn euros (£10.5bn; $17bn) to qualify for more bailout cash, a policy that has sparked growing unrest.
While Germany has contributed the most money to the bailout, BBC Europe editor Gavin Hewitt says its chancellor is held responsible by many for demanding that Greece make swingeing cuts in exchange for the financing it has received.
Ahead of the visit, European Central Bank president Mario Draghi told the European Parliament that Greece had made progress, although "further work" was needed.
Draghi told the parliament's Economic and Monetary Affairs Committee on Tuesday: "It's quite clear that the progress at the level of undertaking the necessary policy reform has been perceptible and significant and it's also clear that more needs to be done."
Mrs Merkel arrived in Athens on schedule at 13:30 local time (10:30 GMT) to be met by Prime Minister Antonis Samaras.
Police have banned protests on Tuesday in much of central Athens, and within a 100m radius of the route Mrs Merkel's motorcade will travel.
However, outside the lockdown zone, thousands of people have gathered, some carrying banners with slogans such as "No to the Fourth Reich".
A three-hour strike has also been called for the beginning of the afternoon.
Mrs Merkel will be in Athens for about six hours, and will hold talks with Samaras, followed by a joint press conference and then a meeting with President Karolos Papoulias.