The European migrant crisis in latest days put pressure on some northern Italy cities, where hundreds of people gathered after being rejected at the country's borders with France and Switzerland.

Some 3,200 migrants and refugees were registered in Milan, Italy's second largest city, and local authorities did not rule out to host some of them in tents, for all available structures were full, local media reported.

"We have to manage an emergency that is structural, and European," La Repubblica newspaper cited Milan mayor Giuseppe Sala as saying.

"We monitor the arrivals, and do not rule out the tent solution, since there are at the moment no other spaces available in such a short time," Sala said.

However, Sala warned against exaggerating the emergency, and explained the new tents would be eventually put within already existing facilities hosting migrants.

"No tent city will be built. Authorities have the situation under control," he said.

The mayor added he was in touch with Italian Defence Minister Roberta Pinotti to verify if dismissed barracks might also be used to host new arrivals, La Repubblica reported.

The sudden increase in the number of migrants and refugees in Milan resulted from a "reflux" of people coming from the near city of Como, after being rejected at the Swiss border, and from near the French border, Sala explained.

Indeed, the situation has also been tense for days in Ventimiglia, few kilometres from France.

Tightened controls at the French border have forced at least 550 people, many of whom are from Eritrea, Sudan, and Ethiopia, to be stuck in the Italian small border town last week.

Frustration grew among the migrants, all of whom were headed towards other European countries.

On Saturday, some 140 of them tried to make their way running through the border, someone even trying to swim in a desperate attempt to reach the French soil, but were pushed back.

Later in the day, activists of the No Border group supporting migrants clashed with Italian police.

"The situation must be decompressed, and the only way to do it is by moving people elsewhere," Italian police chief Franco Gabrielli told state RAI TV, after visiting Ventimiglia on Monday.

Interior Minister Angelino Alfano also addressed the problem.

"Ventimiglia will not be our Calais," he told La Repubblica on Monday, referring to a neglected, makeshift camp in the French northern city where thousands of migrants live while trying to reach Britain.

According to the minister, Italian police so far well managed the delicate situation in Ventimiglia, where conditions are extremely dependant on what happens at the borders with France and Switzerland.

"This must be very clear: if Ventimiglia has not become an Italian Calais yet, this is due to the fact that we have carried out railway controls, and not only those, able to reduce the flow of people," Alfano said.

"At the same time, we have kept sorting out migrants stuck in Ventimiglia into other centers across the country," he explained.

Some 100,244 migrants have arrived in Italy from January to Aug. 8, almost in line with the 100,179 registered in the same period of 2015, Interior Ministry data showed.

Also more than 1,200 people have been rescued in the central Mediterranean between Aug. 5-8, the International Organization for Migration reported.