The US government and Ivanka Trump on Monday expressed sympathy with worshippers attacked while leaving a London mosque - while the president himself remained silent.
May said "The early assessment by police is that the attacker acted alone", and said the incident was "every bit as sickening as those that went before" in London and Manchester.
Deputy Assistant Commissioner Neil Basu said, "The attack unfolded whilst a man was receiving first aid from the public at the scene".
Police declared it was being treated as a terrorist incident shortly afterwards at 00:29hrs. Police have not yet confirmed the suspect's identity.
Trump hasn't *yet* commented on London attack.
The van driver, described by eyewitnesses as a large white man, was detained by members of the public after the attack in Seven Sisters Road at 12.20am on Monday.
Monday morning the Muslim Welfare House headlined its website with this message: "All of us at Muslim Welfare House sends our thoughts and prayers to the victims and those injured in the major incident at Finsbury Park". After the Westminster attack in March it took police just over two hours to do so.
Mr Osborne is understood to have grown up in Weston-super-Mare, Somerset, and have four children, the BBC reports. An hour after police arrived, one resident wrote on Twitter that "agitated" bystanders were classifying the incident as terrorism and questioned the media response.
"We have taken steps because we do believe there is a threat there, but I think overwhelmingly it's nothing to panic about".
She later visited Finsbury Park Mosque where she held talks with faith leaders.
A man identified only as Mohammed who was holding the suspect down told Britain's Guardian newspaper, "The imam came from the mosque and he said, 'Listen we are fasting, this is Ramadan, we are not supposed to do these kinds of things so please step back'".
Britain's terrorist alert is set at "severe", meaning an attack is highly likely, Sky News reported.
Earlier this month on London Bridge, Islamic extremists used a vehicle and then knives to kill eight people and wound many others on the bridge and in the popular nearby Borough Market area.
Manchester was also hit on May 22 when a suicide bomber killed 22 people at an Ariana Grande concert.
"An emergency meeting has been called with our local police commander and local authority to review security concerns for our mosque and others in Tower Hamlets".