ASUNCION, Oct 1 (Reuters) - Paraguay's Congress declared a national emergency on Thursday as forest fires raged, burning vast swaths of the Chaco dry forest, home to sprawling cattle ranches, jaguars and many indigenous tribes.

The emergency declaration boosts funds for fire-fighting and opens the door to requesting international aid to tame the blazes, which have sprouted up throughout the country.

Authorities said two firefighting aircraft had arrived in the country and would douse the most heavily impacted regions.

Regional neighbors Argentina, Bolivia and Brazil are also struggling to contain fires that threaten to reach historic levels amid drought and dry weather.

In Paraguay, the National Emergency Secretariat (SEN) said it had detected 5,231 fires in 24 hours, most in the heavily forested Chaco region.

SEN chief Joaquin Roa called the region a "breeding ground ...for forest fires," with no rain expected and air temperatures soaring.

"All the fires that have been generated are controlled but we have not won the battle, we cannot lower our guard," Roa said.

Paraguay's Directorate of Meteorology said it did not expect rain to fall until Oct. 7. (Reporting by Daniela Desantis; writing by Dave Sherwood; Editing by Sandra Maler)