"Four people died on the spot, while three others were seriously wounded," said local police chief Peterson Maelo. "Those injured have been taken to Nairobi for treatment."
A total of five Germans, four Americans and two Czechs were reported on board the aircraft.
Catherine Ochola from Flying Doctors Service -- an air ambulance service said three "more critical patients" had been flown to Nairobi. A second air ambulance airplane rescued other passengers, and the rest by Kenya's air force.
The pilots' nationalities were not known.
Michael Koikai, a warden with Kenya Wildlife Service, said that the plane had crashed shortly after takeoff from the Ngerende airstrip around midday.
Kenya Civil Aviation Authority official Mutia Mwandwika said the plane belonged to the local air company, Mombasa Air Safari. A company official confirmed the crash but did not provide further details.
The aircraft, a Czech-made twin-turbo propeller LET-410, can carry between 17 and 19 passengers.
The Maasai Mara, some 250 kilometres (155 miles) southwest of the capital Nairobi, is one of Kenya's most popular safari destinations for its currently ongoing annual migration of wildebeest, attracting tens of thousands of tourists to the park.
Wildebeest, zebras and gazelles cross rivers infested with crocodiles as part of an annual migration within the region.
Many tourists choose to fly into hotels or luxury tented camps landing on simple dirt airstrips, rather than brave the long drive on often poor roads from Nairobi.
It stretches for over 1,5000 square kilometres along the border with Tanzania -- forming a single ecosystem with the neighbouring Serengeti -- and in 2011 hosted nearly 300,000 visitors, generating some $30 million in revenue, according to official figures.