The Guinea-Bissau army said Friday it launched a coup bid in the notoriously unstable west African state because of an alleged secret military deal signed by the government with Angola.

The statement, broadcast on national radio, was the first comment from the military since troops attacked the prime minister's residence and seized ruling party headquarters and the radio station on Thursday.

However, it did not specify who was in control of the coup-plagued country on Friday.

"The events of yesterday (Thursday) occurred because we discovered the existence of a secret military accord signed by Prime Minister Carlos Gomes, interim president Raimundo Pereira, the government of Guinea-Bissau and Angola," the statement said.

"This accord aims to legitimise the presence of foreign troops, namely the Angolan military mission, in order to protect the government in times of crisis," it said.

The presence of Angolan troops has been a bone of contention between the government and the army in Guinea-Bissau, which like Angola is a former Portuguese colony.

The troops, said to number about 200, were first deployed last year but Angola said this week they would be withdrawn soon.

Guinea-Bissau timeline
Bissau (AFP) April 13, 2012 - Key dates in the history of the west African state of Guinea-Bissau after the military staged an apparent coup:

- 1974: Independence from Portugal after years of agitation by nationalist leader Amilcar Cabral.

- 1980: The first of several coups, in which Cabral's brother is ousted by his prime minister Joao Bernardo Vieira. The latter goes on to hold, and win, elections.

- 1998-99: Civil war, which culminates in Vieira being ousted in a new military coup, again followed by elections. Kumba Yala wins the presidency.

- 2003: The army mounts another coup, ousting Yala.

- 2005: Returning from exile, Vieira once again becomes president after a new election.

- March 2009: The army chief of staff is killed, which leads to an apparent revenge attack in which President Vieira is assassinated by soldiers.

- July 2009: Malam Bacai Sanha wins the presidency.

- April 1, 2010: New military rebellion.

- December 2011: Yet another military revolt, described as an attempted coup by the government.

- January 2012: Ill, President Sanha dies in a Paris hospital. Raimundo Pereira, the speaker of parliament, becomes interim president.

- March 18: First round of a new presidential election. Former prime minister Carlos Gomes Junior is announced as the winner with almost 49 percent of the vote, but his opponents allege massive fraud.

- April 8: The Supreme Court throws out a bid to have the March 18 vote declared invalid. Three days later, the second-round vote is postponed from April 22 to April 29.

- April 12: Yala calls for a new boycott of the upcoming vote. A few hours later, a new coup attempt breaks out.