Armed Spanish riot police have clashed with protesters trying to hold a demonstration in Madrid against the government's economic policies.

Television reports showed objects being thrown and officers armed with batons hitting protesters near the interior ministry late on Thursday night. Seven police officers were injured.

A police spokeswoman declined to say how many protesters were hurt but said four demonstrators were detained for alleged public disorder, including Gorka Ramos, a reporter for lainformacion.com. The news outlet reported on its website that 13 protesters were treated for injuries and that Ramos was being held in a Madrid jail, unable to speak to his family or employer.

Images of Ramos were published showing him with blood on his face, as he was led away by riot police. Ramos had been carrying identification and was covering the protests live through Twitter, lainformacion.com said.

Protesters angry about the government's austerity programme during Spain's economic crisis have been demonstrating for four days in Madrid. Police have been preventing them from re-erecting a protest camp in the central Puerta del Sol square where they had held protests since May.

Some of the demonstrators are known as indignados (the outraged). They have protested over Spain's current high unemployment, and demanded more democracy, a new electoral law and an end to political corruption in the country.