BERLIN (Reuters) - German police in the western city of Cologne used water cannon on Sunday on left-wing radicals protesting against a rally held by about 600 supporters of the xenophobic "Hooligans Against Salafists" (HOGESA) group.

The roughly 10,000 counter-demonstrators vastly outnumbered those at the HOGESA rally itself where speakers called for Germany's borders to be closed and a ban on building mosques.

Germany is struggling to cope with the arrival of an expected 800,000 to 1 million refugees and migrants this year, many from war zones in the Middle East, and politicians have expressed concern about a potential rise in right-wing radicalism.

At the event in Cologne, scuffles broke out between police and left-wingers before water cannon were turned on to separate the two sides, said police.

After outbreaks of violence at a similar event last year which left several people injured, police stepped up their presence and sent some 3,500 officers to the western city.

HOGESA is a group of self-styled football hooligans and includes right-wing militants and neo-Nazis. Security forces have warned about increased street violence between rival groups.

Last week, the anti-Islam grassroots PEGIDA (Patriotic Europeans Against the Islamisation of the West) group held its biggest rally in months in the eastern city of Dresden, spurred on by the refugee crisis.

Police have warned about an increased risk of racist attacks on politicians helping refugees and say some 285 offences against asylum seekers' shelters had been reported in the third quarter alone, compared with 198 for the whole of last year.

The concerns about growing radicalism coincide with a drop in popular support for conservative Chancellor Angela Merkel for her handling of the crisis and with a rise in the popularity of the anti-immigrant Alternative for Germany (AfD).

(Additional reporting by Reuters TV; Reporting by Madeline Chambers; Editing by Ros Russell)