UPDATE 3-Mexican president's COVID-19 diagnosis raises questions over pandemic management

* Lopez Obrador traveled on commercial flight hours before announcing infection

* Dined with some of Mexico's corporate titans on Friday

* Several ministers take tests, isolate (Adds details of industrialists at dinner, poll quote)

MEXICO CITY, Jan 25 (Reuters) - Mexican President Andres Manuel Lopez Obrador's announcement that he had COVID-19 just a few hours after taking a commercial flight has raised fresh questions over his handling of the pandemic and set off a scramble by top officials to get tested for the virus.

The 67-year-old Lopez Obrador, who has a history of heart problems and high blood pressure, said on Sunday evening he was being treated for mild symptoms of COVID-19 after touring parts of northern and central Mexico for three days.

News of his diagnosis capped the deadliest week of the coronavirus pandemic in Mexico and left questions unanswered about how he became ill following a busy schedule of meetings and public events in the preceding days.

Foreign Minister Marcelo Ebrard, Interior Minister Olga Sanchez and Security Minister Rosa Icela Rodriguez were among top officials who said they had taken tests after the news, while others said they would go into self-isolation.

Standing in for him at a regular daily news conference on Monday, Interior Minister Sanchez said the president was feeling well and remains firmly in charge of the government.

"He will recover soon," she said.

Lopez Obrador's 7 a.m. news conferences have dominated politics in Mexico since he took office in December 2018.

He was at a dinner at the home of aide Alfonso Romo on Friday night that was also attended by some of Mexico's most powerful industrial titans. The guests included cement giant Cemex's chairman Rogelio Zambrano and Armando Garza Sada, chairman of conglomerate Alfa, according to media reports.

A Cemex spokesman said the company did not comment on personal issues. Alfa did not immediately respond to a request for comment.

Footage broadcast by newspaper El Universal showed the president getting on a plane from the central city of San Luis Potosi on a flight which arrived in the capital close to midday on Sunday. Some 6 1/2 hours later he revealed he had COVID-19.

Hector de Mauleon, an El Universal columnist and frequent critic of the president, said on Twitter that Lopez Obrador had been highly irresponsible to get on the plane if he was not feeling right.

RISING POPULARITY

Mexico, which has registered nearly 150,000 fatalities from COVID-19, has the fourth-highest death toll worldwide, and Lopez Obrador's management of the crisis has drawn heavy criticism from political adversaries and many medical experts.

Nevertheless, some polls show his popularity has risen during the pandemic, despite accusations he downplayed it at the start and has put himself in situations of unnecessary risk.

Roy Campos, head of polling firm Consulta Mitofsky, said the public reaction to the president's COVID-19 diagnosis test would likely split along partisan lines, with supporters rallying behind Lopez Obrador and critics going after him.

But, with many Mexicans struggling to get medical care due to hospitals being stretched in the pandemic, it could become more of a problem if awkward revelations emerged about when the president felt unwell and how he acted thereafter, Campos said.

Jose Luis Alomia, a senior health ministry official, said on Sunday evening that the president's symptoms began on Sunday and that he was being continuously monitored.

Lopez Obrador, who was a heavy smoker until he quit after suffering a serious heart attack in 2013, took a telephone call with Russian President Vladimir Putin on Monday to discuss the possible acquisition of Russia's Sputnik V coronavirus vaccine.

Health ministry officials have begun tracing the president's recent contacts. Several of his close aides have had the virus and the president has always insisted that he is in good health. (Interactive graphic tracking global spread of coronavirus: https://graphics.reuters.com/world-coronavirus-tracker-and-maps/)

(Reporting by Stefanie Eschenbacher and Dave Graham; Editing by Paul Simao and Alistair Bell)