Opposition leader Aung San Suu Kyi has suspended campaigning for Myanmar's upcoming by-elections after falling ill, her party said Sunday.

Nyan Win, the spokesman for Suu Kyi's National League for Democracy, said the rigors of crisscrossing the country to attend election rallies had taken a toll on the 66-year-old old Nobel Laureate.

"She was sick, but her health condition has improved now," he said. "She still feels a bit tired."

Suu Kyi, who was released from years under house arrest in 2010, is expected to resume travel once she feels better.

Her party has submitted candidates for all 47 seats up for grabs in the April 1 by-elections, after boycotting previous elections.