ISTANBUL - Istanbul is planning to issue a 500-600 million euro ($550-$660 million) green bond abroad to finance building a metro line, a top local official said on Thursday.

If approved by markets authorities, the issue would be the first green paper from a Turkish municipality, Can Akin Caglar, general secretary of the metropolitan municipality of the country's largest city, told Reuters in an interview.

The metro line is in the southwestern part of the city - home to around a fifth of Turkey's population of 85 million - Caglar said, adding that the project is expected to cost 872 million euros ($963 million) in all.

Caglar, who used to head Turkey's largest state lender Ziraat Bank and was on the board of the BDDK banking watchdog, said getting permissions for such projects and financing was difficult.

Although the municipality had already borrowed 2 billion euros from abroad, some projects had been waiting for authority approvals for years.

"We are also planning to set up a solid waste incineration plant with $500 million (of green money). The permission procedures still continue. We have been working on this for a few years now," he said.

($1 = 0.9069 euros)

(Reporting by Ebru Tuncay and Birsen Altayli Writing by Ezgi Erkoyun; editing by John Stonestreet)