BERLIN (Reuters) - The European Union must seek a deal with countries across Africa's desert Sahel region if it wants to curb an influx of migrants, rather than focusing on bilateral deals with individual countries, the president of Chad said on Wednesday.


President Idriss Deby was speaking in Germany where he met Chancellor Angela Merkel after her trip this week to Mali and Niger - two of the five countries which form the G5 Sahel security organization.


Chad, Burkina Faso and Mauritania are the three other members of the Sahel group of countries, which stretches 4,200 km (2,600 miles) across northern Africa, from the Atlantic in the west to the border of Sudan in the east.


"We can only resolve the issue if we involve the G5 frontline states, not through country by country agreements," Deby, the first head of state from Chad to visit Germany. "That is the only possibility to slow the flow of migration."


He said working with the G5 countries would also enable progress on issues such as drug and human smuggling and terrorism in the remote deserts of the Sahel, which host several jihadist groups.


Deby, current chairman of the African Union, said 90 percent of the refugees transiting through Niger also crossed into neighboring Chad on their journey north to the Mediterranean since the Niger route was closed by militant groups.

Merkel, who has said she will make Africa a priority for Germany's G20 presidency next year, noted that EU officials have set up a G5 Sahel strategy that emphasized the need to deal with the countries as a group.

"That means other EU countries will have to get engaged, also with the cooperation of the commission," she said.

Merkel told reporters that Germany would boost its development aid to Chad by 8.9 million euros to help address water- and food supply issues, noting that it was dealing with over 700,000 refugees from neighboring countries.

Italian data on sea arrivals so far this year show a sharp increase in migrants from several African countries including Mali, Senegal and Nigeria.

The EU last year launched a $2 billion fund for Africa to combat the poverty and conflicts driving people to migrate to Europe. It has also proposed making development aid conditional on governments' cooperation in curbing migration.

(Editing by Dominic Evans)