Two major newspapers here today received messages, attributed to leftist guerrillas, threatening to kill the hostage Mexican ambassador at the occupied Dominican Republic Embassy if the Columbian government did not meet the guerrillas' demands.

There also were reports that three hospitals near the embassy were being partially evacuated. A spokesman at the office of the president refused to confirm or deny the reports, saying "we have nothing official."

The messages put a deadline of 6 p.m., now long since past, for a Columbian response but did not specify when the action against Ambassador Ricardo Galan would be taken. Twelve ambassadors, including Diego C. Asencio of the United States, are among an estimated 32 hostages at the embassy. The siege entered an apparently crucial stage after a fourth round of face-to-face talks this afternoon between the guerrillas and the government.

Late tonight there was no sign of any unusual activity around the embassy.

Reliable sources said the government presented a "a very hard line" during today's talks, in effect telling the M-19 guerrillas that President Julio Cesar Turbay Ayala had decided against releasing any "political prisoners" or paying any ransom money to secure the hostages' safe release, as the M-19 demanded after it seized the embassy Feb. 27.

Both El Espectador and El Tiempo, Bogota's most influential newspapers, received messages over their telex machines while the negotiations were still underway threatening to begin killing hostages -- the first being Galan -- if the government did not demonstrate a more positive attitude in the talks this afternoon.

Enrique Santos, El Tiempo's managing editor, besides describing the telex message, also said he talked by phone to one of the hostage ambassadors and described his mood as "very excited."

Several informed sources had said earlier that the Turbay government would not attempt to retake the embassy by force unless the guerrillas began killing their hostages. These same sources said that if killings began, the government would then send specially trained troops to retake the embassy at whatever cost.

It is understood that the government's only response to the guerrillas' demands thus far has been to offer them safe passage to a country of their choice.

The government issued a communique this evening saying the talks "advanced in a peaceful climate" and that they would continue, although no date for resumption was given.

Turbay was said by informed sources to be in an emergency meeting tonight on the embassy situation with his foreign minister, Diego Uribe Vargas.

There still appeared to be time for either side to change positions and it was believed here that the government was consulting with the 12 governments whose ambassadors are inside the embassy.

Turbay was known to have wanted to play for time, at least until after yesterday's municipal elections.

About 2.6 million Columbians voted, 19 percent of those eligible and the lowest turnout in a recent electoral history replete with low turnouts.

Official figures showed the Liberal Party of Turbay received slightly more than 1 million votes and the Conservative opposition almost 900,000 of the votes counted so far.

Although the Liberals were headed for a majority, "official" lists loyal to Turbay's wing of the party suffered severe setbacks in several areas, including Bogota.