By Monicah Mwangi and Nelson Aruya

NAIROBI, June 8 (Reuters) - Riot police fired tear gas ‌to disperse scores of protesters rallying on ‌Monday against plans to build on part of a ​national park in Kenya's capital.

Officers moved in and arrested at least nine people, including former Chief Justice David Maraga, outside the main entrance ‌of Nairobi National ⁠Park, Reuters reporters said.

The Kenya Wildlife Service has defended the project, saying ⁠it will expand an animal orphanage on the site, Africa's only wildlife reserve within a ​capital city.

Protesters - ​who waved placards ​marked with "Nature is ‌not vacant land" and other slogans - say the plans, including a parking area for more than 1,000 vehicles, will encroach on one of Kenya's most famous protected areas.

The park lies ‌just 10km (6 miles) from ​Nairobi's central business district. Rhinos, ​lions, buffalo ​and leopards can be seen against ‌the backdrop of the ​city's skyline.

"We ​are gathered here because Nairobi National Park is once again under threat," activist Nyaguthii ​Chege told ‌reporters at the scene.

(Writing by George Obulutsa ​and Vincent Mumo Nzilani;Editing by Alexander ​Winning and Andrew Heavens)