AACHEN, Germany (Reuters) - Germany needs to take action now to prevent a re-run of 2015, when some 890,000 migrants arrived in the country, Chancellor Angela Merkel’s Social Democrat challenger for a September election told Reuters on Sunday.

Germany's Social Democratic Party SPD candidate for chancellor Martin Schulz holds a speech during an event at the SPD headquarters in Berlin, Germany, July 16, 2017. REUTERS/Hannibal Hanschke

In September 2015, Merkel threw open Germany’s borders to thousands of migrants to avoid a humanitarian disaster - a move that later hit her popularity and boosted the anti-immigrant Alternative for Germany (AfD), though her conservatives have since recovered and support for the AfD has dropped.

Martin Schulz, whose Social Democrats (SPD) are lagging far behind Merkel in the polls ahead of a Sept. 24 election, warned against a repeat scenario after more than 93,000 mainly sub-Saharan African and Bangladeshi migrants have arrived by boat in southern Italy so far in 2017, up 17 percent on the same period last year.

“The numbers in Italy are worrying - thousands per day,” he said in an interview in the western German city of Aachen.

“If we don’t want a repeat of what we experienced in 2015 we need to take action now as the Italians are reaching their limit in terms of what they can do.”

Other European Union countries need to help Italy, such as by taking in refugees, he added.

Schulz said he had spoken to European Commission chief Jean-Claude Juncker on Sunday about what financial or logistical help Brussels might be able to offer countries prepared to take in refugees and said he would speak to both the Italian government and the Commission about this during the week.

In an interview with the Bild am Sonntag newspaper, Schulz said the situation was “highly explosive” and suggested he wanted to turn it into an election campaign issue, saying: “Those who play for time and try to ignore the topic until the election are acting in a very cynical way.”

Migrant arrivals in Germany have been far lower this year than in the previous two years, with data from the Interior Ministry showing the number of new arrivals seeking asylum fell to 90,389 in the first half of 2017, about half as many as in the year-earlier period.

Last year, some 280,000 migrants arrived in Germany - a sharp drop compared with 2015 - and the refugee issue has not yet played a major role in the election campaign.

The latest Emnid poll showed Merkel’s conservatives on 38 percent and the SPD on 25 percent.

Horst Seehofer, leader of the Christian Social Union (CSU) - the Bavarian sister party to Merkel’s Christian Democrats (CDU) - told the Welt am Sonntag newspaper the situation was calm now but added: “We all know that the wave of migrants will continue.”

The CSU, which takes a tougher tone on migrants than Merkel’s CDU, has long called for an upper limit on the numbers arriving and Seehofer on Sunday repeated his call for a cap of 200,000 per year. Merkel has rejected a cap.

Bild am Sonntag said Schulz would travel to Italy on Thursday to meet Italian Prime Minister Paolo Gentiloni.