Britain and France have increased patrols near mosques and other places of worship following the deadly attack in New Zealand in which 49 people were killed and 42 injured as people attended Friday prayers in two mosques in Christchurch.

British counter-terrorism officers are ready to help their counterparts in New Zealand to investigate the shootings, Britain's most senior counter-terrorism officer said.

"Our international network of UK counter-terrorism officers will be ready to support our counterparts in New Zealand in responding to and investigating this appalling attack," Neil Basu, the British National Policing lead for Counter-Terrorism,said in a statement.

Mr Basu said patrols would be stepped up near mosques in the UK and advice would be given to communities from all faiths about how to protect themselves and places of worship.

French authorities have also stepped up security measures near religious sites, Interior Minister Christophe Castaner said.

"Patrols will be held around religious sites," Mr Castaner said on his official Twitter account.

France is home to the largest Muslim minority population in Western Europe and suffered deadly Islamist militant attacks in 2015 and 2016.

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