Prime Minister Theresa May announced the threat from international terrorism is now critical following the attack in London's Parsons Green Tube Station during rush hour on Friday.
Thirty people were injured as a result of the explosion which left most with minor injuries. Three people remain in hospital, said the London Ambulance Service, while the others have been released.
Mr Andronov said: "The ‘critical’ threat level suggests a further attack on the UK is imminent.
"There is no specific intelligence to indicate that there is any specific threat to Northamptonshire, however, this cannot be discounted, and I want to take this opportunity to reassure our communities that we are responding to the raised threat level, and doing all we can to protect the public.
"We will be focussing additional high visibility patrols in the coming days in crowded places, transport hubs and large events.
"Unarmed officers will be supported by overtly armed police officers on patrol in some places, in the way we did following the Manchester bombing earlier this year. This is aimed at deterrence and increasing intelligence, reassurance and engagement with the communities we serve."
An 18-year-old man was arrested on Saturday on suspicion of terror offences and held in Dover by Kent Police, who took him to a local police station.
“We urge the public to remain alert but not alarmed - the police service and our partners are doing everything we can to help protect the security of our citizens, public institutions, critical national infrastructure, and businesses and places," said Mr Andronov.
“Look out for and report any suspicious activity. Anything that seems out of place, unusual or just doesn’t seem to fit in with day-to-day life. It may be nothing, but if you see or hear anything that could be terrorist-related trust your instincts and call us.
“This is why it is important for information about such activities to be passed to the police. Let us decide whether the information you have is important or not. No piece of information is considered too small or insignificant.
“We are aware that following incidents such as this, there can be an increase in hate crimes within our communities. It is communities that defeat terrorism and over the coming days and weeks we will be reaching out to reassure and strengthen bonds with the many diverse communities we serve. We depend on information from the public, who can be our eyes and ears, in our efforts to keep us all safe.
“We understand that people may be fearful of being targeted as they go about their lives, and I want to reassure you that we do support you, and do want to know about any incident of hate crime that takes place.”
To report any suspicious activity to the police call the confidential anti-Terrorist Hotline on 0800 789 321 or in an emergency dial 999.
Following the incident in Parsons Green, British Transport Police is reminding people that we all have a role to play in keeping the rail network safe. They issued the following advice to the public:
Please remain vigilant for anything that seems out of place or unusual on trains or at stations. This could include:
• Someone being somewhere they shouldn’t be, for example trying to get through a door marked ‘no entry’
• An unattended bag
• Someone checking security arrangements, for example filming CCTV cameras at a station
• Someone avoiding rail staff and police officers
• Someone who could be concealing something under their clothing
If you see something that doesn’t feel right, we want to hear from you. Let us decide if what you have seen or what you know is important.
You should tell a member of rail staff or a police officer what you have seen. You can also call us on 0800 40 50 40, or text us on 61016.
In an emergency, always call 999.
British Transport Police will check any information thoroughly. Every day they receive reports about suspicious behaviour or unusual activity from members of the public and take that information seriously.