Greece said on Monday it would have migrant registration centers running by next week, under pressure from EU partners threatening to sideline it from passport-free travel unless it does more to contain refugees.European Union interior ministers have urged Athens to do more to control the influx of migrants, some threatening exclusion from the Schengen zone as the crisis increasingly divides bloc members.Authorities are struggling to manage an increasing flow of migrants arriving on the country's islands, while still navigating an exit from one of the worst debt crises in decades.Defence Minister Panos Kammenos said Greece would meet a mid-month deadline to complete five "hot spot" centers to register refugees on the Greek islands which are closest in proximity to Turkey, and two relocation centers on the mainland."The Defence Ministry has undertaken a pledge to complete the work for the center's by the 15th (of February)," Kammenos told reporters.Greece was the main gateway to Europe for more than a million refugees and migrants who reached the EU last year. It has been criticized for a failure to control the flow of arrivals, which has shown little sign of easing over the winter.So far, just one center, on the island of Lesbos, where many of the migrants are landing by boat, is open. That will be expanded under the scheme.Newly arrived migrants are photographed and fingerprinted at the registration centres then given a period of time to claim asylum or be turned back to their country of origin, part of measures to manage the migrant crisis.Scuffles broke out on Friday and Saturday on the Greek island of Kos between police and a small number of residents protesting at the construction of a registration center for migrants. There were also protests reported close to the northern city of Thesaloniki on Sunday, and rival protests in Pireaus close to Athens on Monday.Residents were worried that the arrangement could be for the long-term, said Kos mayor Georgios Kyritsis. "One wonders if the creation of such facilities may be an incentive for people smugglers," he told Greek Skai TV.