GETTY More than 17,000 terror suspects have been monitored by French authorities in the last month alone

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This could pose a serious threat to Britain, with France just 20 miles (33km) away across the Channel and Islamic State militants known to be targeting London and other regions. The French Senate announced the results of the “Prevention of Radicalism and Regional Authorities” report yesterday, showing 17,393 people have been listed as terror suspects since the beginning of March. A total of 2,046 French citizens fled to Syria and Iraq to fight for terrorist groups in the Middle East, the report also shows - 249 of those are now believed to be dead.

GETTY France has suffered serious terrorist attacks, most notably in Nice and Paris

A breakdown of the report shows 7,400 individuals were reported by the Security Chiefs of Staff, 5,346 by the public and 5,799 individuals were registered by police or gendarmerie. French authorities said they were not all being constantly monitored, rather some were scrutinised at regular intervals. ISIS terrorists have been honing their sights on an attack on a ferry crossing the Channel, according to senior security sources, which has lead to an increase in armed guards at the Calais border.

They believe they can get terrorists into Britain via a ferry Senior security source

The initial threat emerged last summer but, with the hot season fast approaching, it is possible the jihadis have reaffirmed their murderous desires. A senior security source, confirming the attacks had been planned last year, said: “The presence of the police and soldiers near Calais is very alarming – there’s nothing routine about it.

GETTY This could pose a serious threat to Britain, with France just 20 miles (33km) away

“Apparently they are at a high state of alert because there is a fear of jihadists getting on to a ferry headed for Britain and executing people on the ship. “It is also possible that ISIS may have been told security has in the past been reasonably lax so they believe they can get terrorists into Britain via a ferry.” France’s attempts to guard against terror are in tatters after numerous deadly attacks, most notably the Nice and Paris atrocities, which killed more than 200 people combined.

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GETTY ISIS terrorists have been honing their sights on an attack on a ferry crossing the Channel