London - Three men and two women, aged between 16 and 25, have been arrested in Britain under the Terrorism Act, just days before Thursday's summit meeting of Group of 20 (G20) nations, police said Monday.

Police said the arrests were made over the weekend in the port city of Plymouth, south-west Britain, after a man was caught painting graffiti on a wall.

However, police would neither confirm nor deny media reports that the arrests were linked to demonstrations planned in London against the G20 summit later this week.

Spokesman Netherton said a number of imitation firearms, devices which were made up of fireworks and "some literature relating to political ideology" were found in house searches.

The devices were "probably not lethal," said Netherton, adding: "Fireworks do have an explosive component to them but of a minor nature."

The suspects would continue to be held while further searches were carried out.

However, police stressed that the group was not linked to "any particular religious group" but centered around "political activity involving British nationals."

British police have said they face a "huge challenge" from anti-globalization protestors expected to join demonstrations in the British capital later this week.

Police fear the rallies, on April 1 and 2, will be hijacked by anarchists intent on sparking violence and riots, with thousands of hardline protestors expected to fly in from abroad.

Media reports said anarchist groups from France, Italy and Germany were planning to travel to London for the protests on Wednesday. (dpa)