European security chiefs struggled over solutions to the migrant crisis and oversaw a simulated terrorist attack on a stadium Tuesday, with U.S. Attorney General Jeff Sessions looking on.

Elite police forces staged the anti-terrorism exercise in the French city of Lyon as part of meetings of interior ministers of six European countries plus Morocco. Sessions didn’t speak publicly at the event.

Countering terrorism, including dealing with the return of foreign fighters from Syria and Iraq, was a main topic at the closed-door meetings. The touchy subject of migration, another focus, had officials differing sharply over how best to tackle mass migration given the open internal borders within the European Union.

Poland’s interior minister, Joachim Brudzinski, said European countries are coming around to his nation’s view that “migration today, whether it’s legal or illegal, can be a threat to Europe.” He said Italy’s new populist government was among those coming around to Poland’s hard-line position.

“We do need European solidarity,” he told The Associated Press. “But let’s face it: there were some countries which back in 2015 weren’t participating in this huge invitation of people that’s come to Europe and I don’t see why these countries now need to share the burden, share the responsibility of welcoming these people.”

The French hosts of Tuesday’s meeting however are seeking a multi-country solution to migrant arrivals, working with governments around Europe and Africa.

And the European Union’s commissioner for migration, Dimitris Avramopoulos, insisted that “No country in the European Union or out of the European Union can address these very challenging issues alone and we are ready to continue our cooperation.”

He promised EU support for Italy as “one of the front-line member states that has suffered a lot during the last few years.”

Italian Interior Minister Matteo Salvini maintained his tough stance on migrants, saying later that his country “won’t be considered a refugee camp anymore.” The populist coalition government Salvini is part of has refused to allow migrant rescue ships that aid groups operate on the Mediterranean Sea to dock in Italy.

Salvini said that before he was in position to govern, members of his League party “were considered racists, populists, ignorant. Now, the Italian model of migration management and of closing ports when necessary is becoming popular.”

With Italy refusing to open its ports to ships that take on passengers from sinking or stranded rafts, Morocco is increasingly becoming a springboard for Europe-bound migrants who use the Strait of Gibraltar to get to Spain. The interior ministers of Spain and Morocco are attending the Lyon meetings.

Also present were the interior ministers of Britain and Germany, along with Sessions and U.S. Deputy Homeland Security Secretary Claire Grady.

Sessions’ appearance comes after U.S. President Donald Trump decided not to fire Assistant Attorney General Rod Rosenstein, despite Trump’s anger over the U.S. probe into Russian interference in the 2016 U.S. election.