Britain was on heightened alert Friday following an attack outside a Manchester synagogue that killed two people, as police said they may have shot victims as the terrifying assault unfolded.

Prime Minister Keir Starmer, who visited the scene of the car ramming and stabbing spree in the northwest English city, said security would be boosted at synagogues nationwide as calls to protect Britain's Jewish community intensified.

Thursday's attack, which also left three wounded, took place on Yom Kippur, the holiest holiday of the Jewish calendar. Police said they had shot the attacker dead and declared it a "terrorist incident."

On Friday Greater Manchester Police (GMP) announced one of the two Jewish men killed may have been shot by officers while another non-fatal victim "also suffered a gunshot wound".

GMP Chief Constable Stephen Watson said an interior ministry pathologist had "provisionally determined that one of the deceased victims would appear to have suffered a wound consistent with a gunshot injury."

Noting the attacker, named as Jihad al-Shamie, was not believed to have had a gun, Watson said the injury "may sadly have been sustained as a tragic and unforeseen consequence" when officers ended the "vicious attack."

He added the condition of the hospitalized victim – who "medical professionals" have advised also suffered a gunshot wound – was not life threatening.

Two others in hospital remain in a serious condition, police said.

In a televised statement, Starmer – who was accompanied by his Jewish wife Victoria as he visited the scene – vowed to do everything in his power to protect the Jewish community.