Greater Manchester Police said officers had been called to Heaton Park Hebrew Congregation Synagogue in the north Manchester district of Crumpsall after a witness said they had seen a car driven at members of the public and that one man had been stabbed.
Armed officers responded and a man, believed to be the offender, was shot, GMP said in a statement.
A bomb disposal unit was summoned and was now at the scene, police said.
A video shared on social media and verified by Reuters showed police shooting a man inside the synagogue's perimeter, while another man lay on the floor in a pool of blood, appearing to wear a traditional Jewish head covering.
According to the local newspaper Manchester Evening News, a cordon has been set up following the stabbing, and a major road had been closed while police officers attended.
Prime Minister Keir Starmer said police were being deployed to synagogues across the UK, after the Manchester incident.
"I'm already able to say that additional police assets are being deployed to synagogues across the country, and we will do everything to keep our Jewish community safe," Starmer said on Thursday.
A Reuters photographer said there was a heavy police presence in the area. Ambulance crews were seen in protective body armour and helmets, and at least one person was seen being taken into an ambulance.
The North West Ambulance Service said they had dispatched resources to the area.
"We are currently assessing the situation and working with other members of the emergency services," the ambulance service said.
Andy Burnham, the mayor of Manchester, said it was a serious incident.
"I would say to people listening, firstly to avoid the area - it is a serious incident, but at the same time I can give some reassurance immediately to people that the immediate danger appears to be over, and Greater Manchester Police have dealt with it very quickly," he told BBC radio.
with AP
