LONDON (AFP) - British police arrested three men on Monday in central London on suspicion of Islamist-linked "terrorism", following a series of arrests last week.

The three, aged 21, 24 and 25, were arrested in an "investigation into the commission, preparation or instigation of acts of terrorism", the police said.

Five other men were arrested last week after the police said they had averted a "significant plot". Two of those were later released. The British media have described one of the men arrested last week as a medical student who had travelled to Syria.

A business in west London and four homes in north-west London were searched in the latest investigation, the police said.

The government estimates some 500 British men have joined the Islamic State in Iraq and Syria, and has expressed concern that fighters could return after being radicalised and cause harm in Britain.

Officials said 103 people have been arrested this year after returning from Syria, five of whom have been convicted.