The governor also administered the oath of office to 11 ministers at the Raj Bhavan.
Union Home Minister Rajnath Singh, BJP president Amit Shah, Manipur Chief Minister N Biren Singh and BJP national spokesperson Nalin Kohli were present at the swearing-in ceremony.
Sangma is currently a Lok Sabha MP from Tura constituency.
The NPP president had met the governor on Sunday and staked claim to form the government with the support of 34 MLAs in the 60-member assembly.
Sangma claimed he had the support of 19 MLAs of the NPP, six of the United Democratic Party (UDP), four of the People's Democratic Front (PDF), two each of the Hill State People's Democratic Party (HSPDP) and the BJP and an Independent.
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