In January 1975, Sheikh Mujibur Rahman introduced one-party socialist rule under BAKSAL. Rahman banned all newspapers except four state-owned publications, and amended the constitution to increase his power. He was assassinated during a coup on 15 August 1975. Martial law was declared, and the presidency passed to the usurper Khondaker Mostaq Ahmad for four months. Ahmad is widely regarded as a traitor by Bangladeshis. Tajuddin Ahmad, the nation's first prime minister, and four other independence leaders were assassinated on 4 November 1975. Chief Justice Abu Sadat Mohammad Sayem was installed as president by the military on 6 November 1975. Bangladesh was governed by a military junta led by the Chief Martial Law Administrator for three years. In 1977, the army chief Ziaur Rahman became president. Rahman reinstated multiparty politics, privatised industries and newspapers, established BEPZA and held the country's second general election in 1979. A semi-presidential system evolved, with the Bangladesh Nationalist Party (BNP) governing until 1982. Rahman was assassinated in 1981, and was succeeded by Vice-President Abdus Sattar. Sattar received 65.5 percent of the vote in the 1981 presidential election.