US questions visa waivers for EU nationals

"The majority of these attackers were European citizens with valid passports, so it is easy to imagine any one of them gaining access to this country through a valid visa or through the Visa Waiver Program," said congressman Mike Gallagher.

Nationals from all EU member states - with the exception of Bulgaria, Croatia, Cyprus, Poland and Romania - are allowed to the travel to the US for up to 90 days without having to apply for a visa.

The US administration had added further restrictions on EU nationals who also carry citizenship from Iraq, Iran, Syria, or Sudan.

Others who had travelled to Iran, Iraq, Libya, Somalia, Sudan, Syria, or Yemen after 2011 are also excluded and must apply for a visa.

The fear of returned foreign fighters from battlefields in Syria and Iraq has only further heightened security anxieties.

As of mid-March, around 2,500 EU nationals were thought to be still fighting for the extremists.

However, the EU's top counter-terrorism coordinator has said the biggest threat did not come from returned foreign fighters, but instead from "people who live here and for different reasons become radicalised”.

But earlier this week, the US state department also issued a travel alert for US citizens going to Europe, in light of the recent attacks in France, Russia, Sweden and the United Kingdom.

Gallagher's comments stand in stark contrast to recent announcements by the European Commission that it would not impose visas on visiting US nationals to the EU, despite demands to the contrary from the European Parliament.

The EU commission said it instead prefers to iron out differences with its US counterparts by engaging in dialogue.

In an opinion piece posted on the conservative Fox News network earlier this week, Gallagher said greater efforts need to be made "to close legal pathways by which terrorists enter the homeland."

Gallagher's views are likely to stoke fears that the US may impose even more restrictions on visiting EU nationals, piling on greater pressure for the EU commission to reciprocate with similar measures.

Such demands were also recently floated by the US homeland security secretary, John Kelly.

In April, he said the US should review its visa waiver programme for EU citizens, given the expected military defeat of the Islamic State.

He noted their defeat may trigger a retreat of extremist fighters with EU nationalities back to their home countries.

"We have to start looking very hard at that program - not eliminating it and not doing anything excessive - but look very hard at that program and say, ‘What do we need to do?”', Kelly said.