Mugabe, 84, was one of a dozen state and government heads attending the Somhlolo Stadium celebrations amid tight security. He raised his fist in acknowledgement of the welcome, clearly delighted.

The celebrations went ahead amid heavy criticism in southern Africa that they ignored the plight of the poor, and tight security was ordered.

Some 2,000 people took to the streets Mbabane Thursday in protest at the spending on the party, and the absence of political freedom. Swaziland, a country of around 1 million people, mostly subsistence farmers, is the world's last absolute monarchy.

The '40-40' celebrations were being held to mark the 40th anniversary of Swazi independence from Britain and Mswati's 40th birthday.

Rwandan President Paul Kagame, Lesotho's King Pakalitha Mosisili and US assistant secretary for African affairs, Ambassador Jendayi Frazer were among guests, as were the presidents of Madagascar, Uganda, Namibia, Botswana, Mozambique and Malawi.

Mugabe received the biggest round of applause from assembled citizens and heads of state.

The government says the party is costing 20 million emalangeni (US$12.6 million dollars), but critics estimate it is costing several times that.

The controversy comes against the backdrop of rising tensions in the normally peaceable kingdom in advance of legislative elections on September 19.

Striking workers and youths brandishing sticks and branches smashed car windows and looted shops in Mbabane Thursday in some of the worst rioting in the country in decades.

Mswati, who is famous internationally for having 13 wives, has reigned over the landlocked kingdom for 22 years.