Speaking in Cologne on Sunday at the end of a four-day trip to Germany which highlighted differences, Mr Erdogan said Turks here should learn German but not to give up their Turkish identities. He called assimilation a 'crime against humanity'.

The comments to a huge crowd of some 16,000 people of mainly Turkish origin sparked sharp reactions from Dr Merkel and members of her conservatives, who have long argued that immigrant groups must adapt to the German way of life even if it means abandoning aspects of their native cultures.

'If they are citizens, then of course I expect them to behave as full citizens without qualification. Their loyalties are then to the German state,' Dr Merkel told reporters in Hamburg, when asked about Erdogan's remarks.

'I think further talks with the Turkish prime minister are needed about the meaning of integration,' she added.

Some 2.5 million people of Turkish origin live in Germany, more than in any other country in western Europe. While some are well integrated into German life, others live in separate urban communities, speak only Turkish, and stick to old traditions.

Ali Kizilkaya, head of the German Muslim group Islamrat, praised Erdogan for encouraging Turks here not to forget their culture and expressed disbelief at the criticism.

'A lot of Turks finally got the feeling a government leader was listening to them,' Kizilkaya told Tagesspiegel daily.

'That's something Merkel could do too.'

Integration
Dr Merkel, who opposes Turkey's bid to join the European Union, has made improving integration a priority of her government, bringing a coordinator for the issue into her Chancellery and holding regular 'summits' with leading immigrant groups.

But she has tended to put the onus on immigrants to adapt.

When asked last month why a government 'integration plan' existed only in German, she replied curtly that that was the national language and those who could not read it should learn.

Kurt Beck, head of the centre-left Social Democrats (SPD) which share power with Dr Merkel's conservatives, was also critical of Erdogan, saying his suggestion that Turkish language schools be set up in Germany went in the 'wrong direction'.

However, Greens leader Claudia Roth said she saw nothing wrong with Mr Erdogan's proposal, citing the many English and French language schools in Germany.

Members of Dr Merkel's conservative bloc produced the sharpest responses, with Bavarian premier Guenther Beckstein calling Mr Erdogan's comments 'nationalistic' and accusing him of supporting the 'ghettoisation' of Turks in Germany.

'The task (for Turks) is to be good citizens in Germany, to learn German, to speak German in their families,' he said.

Tensions between Germans and Turks were stoked before Erdogan's trip by a fire in a housing block in the western city of Ludwigshafen which killed nine people with Turkish roots.

The cause of the blaze is unknown but the local Turkish community has speculated it was racially motivated. -- REUTERS