Left-wing guerrillas who seized the Dominican Republic Embassy two months ago flew to Cuba today, freeing their 16 diplomatic hostages and receiving a show of support from many Colombians who cheered them at the airport.

Four of the hostages were freed here before the early-morning departure and the rest, including U.S. Ambassador Diego Asencio, were released in Havana under terms of the accord negotiated with the Colombian government.

The Washington-based Inter-American Human Rights Commission, which mediated the solution, is to post observers in Colombia to monitor current military trials of alleged guerrillas and to observe treatment of such prisoners.

Neither the M19 guerrillas nor the Colombian government announced details of the agreement but it was unofficially reported to include the payment of as much as $2.5 million in ransom from "private" sources not directly tied to governments whose diplomats were held hostage.

The siege began Feb. 27, when the guerrillas burst into a midday cocktail party at the embassy, capturing 57 hostages -- most freed in the interim.

Initially the 16 guerrillas in the embassy insisted on freedom for 311 "political prisoners" and payment of $50 million. They lowered their terms sharply over the course of about 20 negotiating sessions. However, the government of President Julio Cesar Turbay Ayala did not give in to the last principal demand, the release of at least a token number of prisoners charged with subversion, political kidnapings or assassination.

The guerrillas clearly won the admiration and sympathy of many average Colombians during the siege, which was front-page news here daily.

Crowds lined the airport runway today to cheer and wave as the Cubana Airlines plane, sent by the Cuban government as part of the accord, took off about 8:25 a.m. "M19! Return soon," many onlookers shouted.

"Say goodbye to your countrymen," a young father told his infant son as the plane roared overhead.

On board were the 16 guerrillas, Cuba's ambassador to Colombia, a representative of the International Red Cross, and the 12 hostage diplomats: rthe ambassadors of the United States, Mexico, Brazil, Switzerland, Guatemala, Haiti and the Rev. Angelo Acerbi, the papal nuncio, as well as the charges d'affaires of Bolivia and Paraguay and the consuls of Venezuela, Peru and Guatemala.

The ambassadors of Venezuela, the Dominican Republic, Israel and Egypt were released before the plane departed for Cuba, along with two Colombian journalists. Captured at the Dominican Republic national day party Feb. 27, the pair had chosen to stay on, despite earlier offers of freedom by the guerrillas, in order to sell photographs and articles from inside the embassy.

Before today, the M19 had let go 38 of their original hostages. Uruguay's ambassador had escaped by jumping out a second-floor window.

Dominican Ambassador Diogenes Mallol, the host of the fateful party who was set free here, praised Colombian President Turbay for solving "this problem with prudence and calm."

Turbay, noting that no jailed leftists were freed, said, "It was a victory for the legal order." [In Washington, the White House released a letter to Turbay from President Carter saying, "Your firm and patient leadership has achieved its goal: a dignified and peaceful solution. . . . As you know, the United States unequivocally condemns all terrorist acts. I am pleased that our two governments have been able to work so closely together in this common struggle."]

While the siege ended nonviolently, it began with the death of one guerrilla, who was 17, as well as a 20-year-old student caught in the crossfire of the assault.

Although rumors had circulated throughout Bogota for the past 48 hours that a settlement was near, it was not until 5 p.m. Saturday that the hostages inside the embassy were told that they would be leaving this morning, according to Luis Valencia Soto, the Colombian journalist who chose to remain until the takeover ended.

Journalists from at least 15 countries began congregating in an area reserved for them near the embassy, nicknamed "Scoop City," where some had camped in tents since Feb. 27.

Half an hour after sunrise, a caravan of Red Cross vehicles, three ambulances and two buses, with their windows painted over in red, appeared.

As cameras whirred, the vehicles took on the passengers and pulled away at 6:45 a.m. for the airport. It had been closed to all traffic at 4 a.m. and was not reopened until the Cubana plane left.

The human rights commission members rode with the guerrillas and the hostages as added protection against any attempt to stop the departure. Commission President Tom Farer said the M19 commandos had their guns and hand grenades with them as they rode to the airport. Most of them wore the hoods they had used throughout the takeover.

The plane arrived in Havana three hours after takeoff. Asencio left shortly afterward for Florida. The Swiss ambassador reportedly left later for Europe while the remaining diplomats from Latin America were scheduled to return to Bogota on the same Cubana plane that took them to Havana.

The guerrillas had said earlier that they planned to move on to Western Europe, probably Vienna, for a press conference to explain their reasons for seizing the embassy. Today, however, they reportedly said they would stay longer in Havana.

Asencio, for his part, has had lawyers in New York negotiating a book contract.

The political impact of the embassy seige within Colombia is already the subject of analysis. Government supporters were relatively pleased with the outcome, at least initially, since Turbay held firm against releasing prisoners or paying ransom while avoiding a bloodbath.

The guerrillas clearly won sympathy for their causes of revolutionary change and international recognition of the human rights and social problems that exist here. The M19's charges that persons suspected of subversive activities are regularly tortured here were in part corroborated by a report by Amnesty International released 10 years ago.

For the moment, most Colombians probably agreed with Israel's ambassador, Eliahu Barak, who said after his release today: "Thank Good, everything turned out well."