El Salvador's government on Thursday declared an alert for the capital San Salvador and outlying towns over the lack of drinking water, which it blamed on climate change.

"We understand the problem of the lack of water and ask the population to accept our apologies for the effect it is having," President Salvador Sanchez Ceren told a joint news conference with other officials.

The country's Civil Protection service was being used to provide emergency water supplies in the hardest-hit zones with trucks and by installing tanks, said its chief, Jorge Melendez.

The chief of the state's aqueduct and sewerage agency ANDA, Marco Fortin, said four new wells were being drilled in the San Salvador region.

He added that ANDA was currently able to supply only half the water needs of the capital's population of 1.7 million because of shrinking stocks and leaks in the network of pipes.

Environment Minister Lina Pohl said climate change "has caused less rain to fall, diminishing the refilling of groundwater reserves."