Soledad's Mayor Joao Herrera (L) gives a woman, condoms and kits with insect repellent during a campaign to fight the spread of Zika virus in Soledad municipality near Barranquilla, Colombia, in this February 1, 2016 handout photo supplied by the Soledad Municipality. [Photo/Agencies]

BOGOTA - More than 3,100 pregnant Colombian women are infected with the mosquito-borne Zika virus, President Juan Manuel Santos said on Saturday, as the disease continues its rapid spread across the Americas.

The virus has been linked to the devastating birth defect microcephaly, which prevents fetus' brains from developing properly. There is no vaccine or treatment.

There are so far no recorded cases of Zika-linked microcephaly in Colombia, Santos said.

There are 25,645 people infected with the disease in Colombia, Santos said during a TV broadcast with health officials. Among them are 3,177 pregnant women.

"The projection is that we could end up having 600,000 cases," Santos said, adding there could be up to 1,000 cases of Guillain-Barre syndrome, a rare but serious condition that can cause paralysis and which some governments have linked to Zika infection.

Santos said the government was now uncertain about a previous projection for up to 500 cases of Zika-linked microcephaly, based on data from other countries battling the disease. Authorities will continue to investigate, he said.

The government will be working across the country to fight mosquitoes - fumigating and helping families rid their homes of stagnant water, the president said.

Colombian health minister Alejandro Gaviria has said he believes three deaths are connected with Zika.

The province of Norte de Santander had nearly 5,000 cases of the virus, more than any other in the country, an epidemiological bulletin from the national health institute published on Saturday showed.