DAR ES SALAAM, Tanzania (AP) — Five Cabinet members from Tanzania's ruling party have lost their parliamentary seats, according to partial results released Tuesday by the country's election commission.

They lost to candidates representing an opposition alliance of four parties including Chadema, the main opposition party.

Results for the presidential election are trickling in and full results are expected Thursday. Tensions are rising between rival supporters on Tanzania's mainland and on the semi-autonomous island archipelago of Zanzibar, which also voted Sunday.

Tanzania's presidential race is the most tightly contested since this East African country became independent in 1961. The ruling party's presidential candidate, Works Minister John Magufuli, is challenged by former Prime Minister Edward Lowassa, who used to be a high-ranking member of the ruling party until he defected to the opposition after failing to become the ruling party's presidential candidate.

Suleiman Kova, a police commander in Dar es Salaam, said 166 people are being held on allegations they published unofficial poll results on social media.

The voting was largely peaceful but there are concerns that a close final result may spark violence.

In Zanzibar, police deployed heavily in the streets to confront supporters of opposition leader Maalim Seif Hamad of the Civic United Front, who on Monday declared himself the winner of Zanzibar's presidential election. Zanzibar, which is part of the United Republic of Tanzania, is run by a semi-autonomous government.

The Civic United Front has fought for years to win control of the island's administration from the ruling Chama Cha Mapinduzi party, narrowly losing the last election in 2010. On Tuesday the usually busy streets of Zanzibar town were largely empty of people, with many shops shuttered as residents wait for the official announcement of poll results.

Ali Sultan contributed to this report from Zanzibar, Tanzania.