(Reuters) – More than 25,000 migrants arrived in Italy in July, 12 percent more than in the same period last year, EU border agency Frontex said on Friday.

Most of the migrants who made the trip across the Mediterranean from North Africa were Nigerians and Eritreans, Frontex said. The number of migrants arriving in the January to July period was stable compared to last year at 95,000.

Frontex said the quality of the boats people smugglers were using to transport migrants was deteriorating.

“In recent months, poor quality rubber boats accounted for four out of every five vessels used,” Frontex said in a statement.

“Many of the migrants spoke of being forced onto the dinghies and small wooden boats despite fearing for their lives.”

Illegal migrants sit on the dock at the Tripoli port after 117 migrants of African origins, including six pregnant women, were rescued by two coast guard boats off the coast of Libya on June 7, 2016. (MAHMUD TURKIA/AFP/Getty Images)

Barred from travelling further north by closed borders in France and Switzerland, many of the migrants are stuck in Italy.

More than 3,000 migrants are stranded in the financial capital Milan, its mayor said, as Switzerland and France tightened border controls.

Migrant arrivals through Greece were about 97 percent lower in July than last year, mainly due to a European Union deal with Turkey to stem the flow.

(Reporting by Robert-Jan Bartunek; Editing by Janet Lawrence)