Three men and a police officer have been stabbed at a mosque in Birmingham, West Midlands Police have said.
The male police constable was responding to reports that three men had been stabbed inside the mosque in the Ward End area of the city when he was attacked.
The mosque involved is thought to be the Washwood Heath Muslim Centre in Ward End. The four men are being treated in hospital for their wounds and are described as "stable".
A 32-year-old man has been arrested on suspicion of attempted murder and is currently in custody, a police spokeswoman added.
Mohammed Shafiq, the leader of national Muslim organisation the Ramadhan Foundation, said: "The Ramadhan Foundation expresses its deep concern at the stabbing of three people and a police officer in the Ward End mosque in Birmingham last night."
A nearby resident reported hearing an argument coming from inside the mosque and believes it was a domestic incident between members, Shafiq said.
"I have spoken to someone who lives a few doors down from the mosque and they described hearing an argument between some of the people inside the mosque. It escalated into violence and a police officer has been stabbed.
"People, anti-Muslim extremists, are going to try to take advantage of this - it's very serious that a police officer has been stabbed during duty.
"The aftermath of the brutal murder of Lee Rigby has led to an increase of attacks. The involvement of a police officer in this incident obviously causes more concern.
"Our immediate thoughts are with the victims injured and their families.
"It is too early to speculate on the circumstances of the stabbings but we must be clear there should be no place for this sort of violence in our country.
"There will obviously be people who will try to take advantage of this tragedy but we must not allow them to succeed."
The spokeswoman said: "Police were called at 11pm on Saturday night to a mosque in Washwood Heath Road, Ward End, to reports of three men with stab wounds.
"Officers arrived at the incident and whilst the man was being detained, one police officer also suffered a stab wound.
"The three people and the officer have been taken to hospital, all are currently described as stable."
Officers are conducting patrols in the area in a bid to reassure local people, she added.
A cordon is in place while investigations continue.
All three men and the officer were stabbed inside the mosque, the police spokeswoman confirmed.
A number of mosques have been targeted since the brutal murder of Drummer Lee Rigby close to his barracks in Woolwich, south London, last month.
The killing also sparked a huge increase in anti-Muslim incidents in the days that followed, according to the organisation Faith Matters, which works to reduce extremism.
In what were believed to be reprisal attacks, the Islamic Somali Community Centre in Muswell Hill, north London, was burnt to the ground while the Grimsby Islamic Cultural Centre was also targeted by arsonists who threw petrol bombs.
Last week Muslim groups called on authorities to take serious action against anti-Islamic attacks following Drummer Rigby's death.
The Islamic Human Rights Commission (IHRC) said Muslims were scared and living in fear of a ''wave of attacks''.
Massoud Shadjareh, chairman of IHRC, said: ''Muslims feel scared right now and it is completely understandable.
''Muslims have been physically attacked, mosques burnt down, cemeteries vandalised and social media is full of anti-Muslim hatred and violent threats towards Muslims. More needs to be done to protect the Muslim community.''