Tens of thousands of Taiwanese marched in the southern port city of Kaohsiung in support of the governing party's plan to hold a referendum on UN membership.
Police said about 100,000 people joined the march, but organisers - including the ruling Democratic Progressive Party (DPP) said close to 300,000 marched.
Independence-leaning President Chen Shui-bian (centre) and Vice President Annette Lu (right) back the referendum, which Beijing vehemently opposes.
Mainland China considers Taiwan a part of its territory and opposes a separate UN seat or any other symbol of independence for the island.
Supporters of the opposition Kuomintang (KMT) party held their own march in Taichung, in central Taiwan.
The KMT's candidate for next March's presidential elections, Ma Ying-jeou (centre), also wants Taiwan to join the UN, but under its official name, the Republic of China.
The KMT also wants a referendum on the issue. This man's hat says: "Return to the United Nations" and displays the KMT emblem.