This Oct. 29, 2018 photo provided by the U.S. Air Force shows deployers from Headquarters Company, 89th Military Police Brigade, Task Force Griffin get ready to board a C-130J Super Hercules from Little Rock, Arkansas, at Fort Knox, Kentucky, in support of Operation Faithful Patriot. The Trump administration on Monday, Oct. 29, 2018, announced plans to deploy 5,200 active duty troops, double the 2,000 who are in Syria fighting the Islamic State group, to the border to help stave off the caravans. (Airman 1st Class Zoe M. Wockenfuss/U.S. Air Force via AP)

Tapachula/Guatemala City - Hundreds of Salvadorans are travelling through Guatemala and Mexico towards the United States, following two other caravans in defiance of US President Donald Trump's anti-migration stance, a Salvadoran official said Wednesday.

About 200 Salvadorans are waiting in the Guatemalan border town of Tecun Uman to enter Mexico, and 500 others are on their way there, said Antonio Azucar, a diplomatic representative for El Salvador based in the Mexican city of Tapachula near the border.

About 300 Salvadorans entered Mexico on Tuesday, Azucar told Radio Formula.

A first caravan estimated to include between 3,600 and 5,500 Central Americans has meanwhile reached Juchitan in Mexico's southern Oaxaca state.

Another caravan of up to 2,000 people is on its way from Tapachula to Huixtla in Mexico's Chiapas state, which borders Guatemala.

The migrants have pursued their route despite the US deployment of 5 200 troops to the border with Mexico and new threats from Trump on Wednesday.

"Our military is being mobilised at the Southern Border," Trump tweeted. "Many more troops coming. We will NOT let these Caravans, which are also made up of some very bad thugs and gang members, into the U.S. Our Border is sacred, must come in legally. TURN AROUND!"

The US president continued: "The Caravans are made up of some very tough fighters and people. Fought back hard and viciously against Mexico at Northern Border before breaking through. Mexican soldiers hurt, were unable, or unwilling to stop Caravan. Should stop them before they reach our Border, but won't!"