TAIPEI, Taiwan - Holding balloons and waving flags, tens of thousands of Taiwanese paraded throughout the island Sunday to support their favoured presidential candidates less than a week before what is expected to be an extremely tight election.

President Ma Ying-jeou, who has improved relations with rival China during his 3 1/2 years in office, led a large crowd of supporters in a three-mile (five-kilometre) march down a main Taipei thoroughfare.

"If you want peace with the mainland and friendly international communities, join me and let's walk together," the 61-year-old Ma told supporters.

Ma's Nationalist Party said at least 200,000 people joined the Taipei parade. Police did not give an estimate.

Pro-Ma parades were held simultaneously in three other cities.

Polls indicate that Ma is locked in a virtual dead heat with his main challenger, Tsai Ing-wen of the opposition Democratic Progressive party, ahead of Saturday's election.

The 55-year-old Tsai stood on a truck encased with bulletproof glass as she cruised the streets of the southern city of Tainan, waving to prospective voters. Thousands of her supporters also staged a parade in Taichung city in central Taiwan.

During his term, Ma has tied Taiwan's high-tech economy closer to China's vast markets through a series of initiatives, including a far-reaching tariff-slashing agreement and the launching of hundreds of weekly cross-strait flights.

The result has been significantly lowered tensions with China, from which the island split amid civil war in 1949. China still claims the island as part of its own.

Tsai faces mounting skepticism on whether Taiwan could continue the China trade agreements if she is elected. Unlike Ma, she has refused to renounce possible moves to formalize the island's de facto independence, to the ire of China.

However, Tsai has gained wide support by attacking Ma's economic policies, saying they have spurred income inequality and made it difficult for young Taiwanese to afford decent housing.

On Sunday, Tsai said that if elected, she will create a new political culture by formulating policies together with the Nationalists and other opponents.

"We will meet people's expectations for political tolerance, understanding and co-operation," she said.

Though polls have showed Ma holding a tiny edge, a surge by third-party candidate James Soong -- a former member of Ma's Nationalist Party -- would likely take more votes away from Ma than Tsai.