Counter-terrorism police said they discovered a second suspicious package in England's southwest on Saturday, far from where a similar object was found on London's Tube network.

Officers from London's Metropolitan Police swooped on an address in the town of Newton Abbot, in the county of Devon, as part of their enquiries. While there, they found a device that was deemed suspicious and dangerous.

The local Devon and Cornwall Police were alerted to deal with the evacuation of properties around the address, some 270 kilometers (170 miles) from London.

On Friday, armed police used an electric stun gun to arrest a 19-year-old on a busy shopping street in London in connection with the suspicious package found the previous day. The suspect - arrested on suspicion of the commission, preparation and instigation of terrorism acts - remained in custody on Saturday.

A credible bomb attempt?

The package in question, found on a train at North Greenwich Tube station, near London's O2 entertainment complex, was also being examined by forensics officers.

Security was stepped up on the London Underground network, with "The Times" newspaper describing it as "the first credible bombing attempt on the London transport network in more than 10 years."

The terror threat level for Britain has been set at severe - the fourth-highest of five levels - since August 2014 meaning an attack is considered highly likely. Islamist militants struck in London on July 7, 2005, killing 52 people with a coordinated set of suicide bombings.