Counter-terrorism officers in England are investigating overnight attacks on four mosques in Birmingham city following reports that a man with a sledgehammer was seen smashing windows at two of them, AFP reported on Thursday.

Chief Constable Dave Thompson said the motive for the attacks is not known yet. “What I can say is that the [police] force and the counter terrorism unit are working side-by-side to find whoever is responsible,” police said.

The incidents came nearly a week after a 28-year-old Australian citizen opened fire at two mosques in New Zealand’s Christchurch city and killed 50 people last Friday.

Authorities first received an alert at 2.30 am (8 am Indian time) about a man smashing windows with a sledgehammer at a mosque. They received further reports of a similar incident at a mosque in a nearby locality, after which officials began patrols and found more damage at two other locations.

Police are treating the incidents as linked, and are looking to find evidence and examining the closed-circuit television footage.

“The whole of the front windows, about six, were smashed,” a spokesperson for Witton Islamic Centre told BBC about the incident at one of the mosques. “Because of the force he used it’s gone through the windows and into the mosque itself.”

The Birmingham Council of Mosques said: “We were deeply horrified to hear a number of mosques were vandalised during the early hours of this morning. Birmingham’s mosques are a place of worship, serenity and a source of peace and tranquillity. We are appalled by such acts of hate/terror.”

Home Secretary Sajid Javid said: “Deeply concerning [and] distressing to see number of mosques have been vandalised in Birmingham overnight. Police are investigating motive but let me be clear – hateful behaviour has absolutely no place in our society and will never be accepted.”