South Africa and South Rhodesia raided targets inside Zambia on several occasions. Rhodesian counterinsurgency operations extended into Zambia after Zimbabwe People's Revolutionary Army (ZIPRA) rebels shot down two unarmed Vickers Viscount civilian airliners (Air Rhodesia Flight 825 on 3 September 1978 and Air Rhodesia Flight 827 on 12 February 1979) with Soviet-supplied SA-7 heat-seeking missiles. In retaliation for the shooting down of Flight 825 in September 1978, the Rhodesian Air Force attacked the ZIPRA guerrilla base at Westlands farm near Lusaka in October 1978, warning Zambian forces by radio not to interfere. Conflicts with Rhodesia resulted in the closing of Zambia's borders with that country and severe problems with international transport and power supply. However, the Kariba hydroelectric station on the Zambezi River provided sufficient capacity to satisfy the country's requirements for electricity. TAZARA, a railway to the Tanzanian port of Dar es Salaam, built with Chinese assistance, reduced Zambian dependence on the railway line south to South Africa and west through an increasingly war-ravaged Angola. Civil strife in neighbouring Mozambique and Angola created large numbers of refugees, many of whom fled to Zambia. Internationally, Zambia was an active member of the Non-Aligned Movement (NAM), and hosted a summit in Lusaka in 1970. Kenneth Kaunda served as the movements chairman 1970–1973. Among the NAM countries Zambia was especially close to Yugoslavia. Outside the NAM Zambia also had close relations with the People's Republic of China. In the Second Congo War, Zambia backed Zimbabwe and the Congo but did not participate as a belligerent. Multi-party democracy The end of one party rule One party rule and the declining economy created disappointment among the people. Several strikes hit the country in 1981. The government responded by arresting several union leaders, among them Frederick Chiluba. In 1986 and 1987, protests arose again in Lusaka and the Copperbelt. These were followed by riots over rising food prices in 1990, in which at least 30 people were killed. The same year, the state owned radio claimed that Kaunda had been removed from office by the army. This was not true, and the 1990 Zambian coup d'état attempt failed. These extensive protests made Kaunda realise the need for reform. He promised a referendum on multiparty democracy, and lifted the ban on political parties. This resulted in the quick formation of eleven new parties. Among these Movement for Multiparty Democracy (MMD), led by former union leader Frederick