"Today is an important milestone for Salisbury as it emerges from the shadow cast by the use of chemical weapons on the steets of our country," May said.
British Prime Minister Theresa May on Monday praised Salisbury's "resolve" on the one-year anniversary of the poisoning of former Russian spy Sergei Skripal while the Russian embassy in the UK took to Twitter to discredit the official investigation.
"Today is an important milestone for Salisbury as it emerges from the shadow cast by the use of chemical weapons on the streets on our country," May said in a statement.
"The fact Salisbury and the wider region has fought back so well from such a devastating and reckless incident is testament to the resolve, forbearance and positivity of the community," she added.
Former Russian spy Sergei Skripal and his daughter Yulia were poisoned with the Novichok nerve agent on March 4 last year in the southern city of Salisbury. Both survived the attack which the UK and its allies have blamed on Russia — an accusation Russia denies.
May, who visited Salisbury on Monday morning, also met with the father of Dawn Sturgess, who died in July after being exposed to the nerve agent. She also met with Charlie Rowley, Sturgess's partner, who inadvertently poisoned her when he gifted her what he thought to be a perfume bottle he had found on the street.
The visit comes just days after authorities declared that the clean-up operation is now complete and 24 hours after Defense Secretary Gavin Williamson announced that £11 million (€12.8 million) had been allocated to bolster the country's response to chemical attacks.
"Britain and its allies have also demonstrated that they will take a stand against the use of chemical weapons, from the sanctions enforced on Russia following the reckless use of Novichok to the strikes against the chemicals used by the Syrian regime," Williamson said in a statement.
He added: "We recognise we need resilience to face evolving threats which is why we have invested £11 million into ensuring we have world-leading capabilities."
Meanwhile, the Russian embassy in the UK marked the occasion by releasing a report "debunking the British narrative on Russia's "capability, motive and track record"."
In the report, the Russian embassy criticises British authorities for making "quite serious accusations against Russia without presenting any meaningful evidence" and says the investigation "is based on unverifiable statements and artificial constructs."
"Russia has nothing to do with the incident that took place in Salisbury on March 4," the report states.
The incident plunged relations between the UK and Russia to new lows. Britain expelled 23 Russian diplomats with allies including Germany, France and the US taking a similar measure.
Britain has also charged in absentia two Russian men it says are intelligence officers for the Skripals' attempted murder.