The Persian Gulf war escalated today fired long-range, ground-to-ground missiles into two Iranian cities, inflicting heavy civilian casualties in the first use of such missiles since the conflict began 18 days ago.

Iranian charge came as President Saddam Hussein's Iraqi government dispatched five top-ranking envoys on a 27-nation tour of Europe, Africa and Asia in an apparent search for a medicated end to the 18-day-old conflict.

Meanwhile, Iran has begun a counterattack against Iraqi forces in the southwestern oil-producing province of Khuzestan, President Abol Hassan Bani-Sadr said tonight.

[The president said in a broadcast message that Iranina forces under the command of Mostafa Chamran, head of military operations in the province, began their push west of the provincial capital of Ahwaz yesterday afternoon. His announcement could be immediately confirmed tonight.]

A communique issued in Baghdad said Iraqi forces had destroyed power stations and fuel depots at Ahwaz. Iraqi troops also pressed their assault on Khorramshahr and Abadan in the south, and on Dezful farther north. The communique said Dezful was besieged "on all sides."

[U.S. officials in Washington reported, meanwhile, that Iran has received air shipments of military supplies from Libya, another militantly Moslem nation closely allied to the Soviet Union. North Korea earlier was reported to be sending military equipment to the Iranians, who are the object of an embargo organized by the United States].

Iranian spokesmen, according to news agency dispatches from Tehran, said 180 persons were killed and 300 wounded in the Iraqi missile attacks on Dezful and nearby Andimeshk. The official Iranian news agency Paris said four of the missiles crashed into the two towns, while Prime Minister Mohammad Ali Rajai was quoted by Tehran Radio as saying eight of them were fired in "another insane action" by the Iraqis.

The Iranian announcements did not identify the missiles, but claimed each missile weighed 4,400 pounds and had a 40-mile range. Observers noted that this is slightly less than the distance separating the Iraqi border from Dezful, a key rail and road center linking Khuzestan's oil installments with the rest of Iran.

Iraq said nothing about the alleged missile attack. The authoritative International Institute for Strategic Studies in London listed Soviet-made Frog7 and Scud B missiles as the main components of the Iraqi missile arsenal.

The Iranian leader, Ayatollah Ruhollah Khomeini, reacted to the Iraqi attacks with a virulent speech on Tehran Radio vowing that Iranians will defend themselves "with all the means in our power."

"The Iraqis will lose the war," he said, adding that the Baathist government in Baghdad will fall and be replaced by "Islamic" rule.

Saddam Hussein and his top aides are Sunni Moslems in a nation with a strong Shiite Moslem population that reportedly has in recent years become a slim majority. Khomeini's Iran is built on the primacy of Shiite Moslem principles, and he has accused the Baathist leadership in Iraq of godlessness.

The Iranian government, too, reported it was sending envoys to friendly countries and perhaps the United Nations to explain its side of the war. There was no sign, however, that the Iranian and Iraqi missions were coordinated efforts. At the same time, Secretary General Habib Chatti of the Islamic Conference launched a new Moslem attmept at promoting settlement of the war. President Mohammed Zia ul-Haq of Pakistan, who headed an earlier, futile try by the 40-nation conference, said Chatti would visit Tehran and Baghdad.

The Iraqi missian appeared to reflect frustration over being bogged down in Khorramshahr longer than the Army command anticipated. While the government characterized the diplomatic initiative as merely briefings to explain "the grave consequences of Iran's aggressive attitude agains Iraq," attention immediately focused on Turkey as a possible go-between in the territorial dispute over the Shatt-al-Arab waterway that helped trigger hostilities.

Turkey is the only Moslem country in the envoys'intinerary, which includes Soviet bloc nations in Eastern Europe and Third World nations in Asia and Africa.

The government said the envoys will brief heads of state in the 27 nations on the latest development on "the eastern flank of the Arab homeland and (on) Iraq's genuine peace initiative for a cease-fire which the Persians rejected."

The envoys include the speaker of Iraq's National Assembly, Naim Haddad, who will visit Easter Europe; Abdul Fattah and Mohammed Amin; State Minister Hashim Hassan, who will visit heads of state in Africa; and Karim Mahmoud Hussein, who will visit Turkey and Greece.

The Iraqi Army, meanwhile, in an apparent attempt to offset reports of its inability to capture all of Khorramshahr, today put on display numerous weapons it said it captured from Iranian forces embattled on the northeastern front. Correspondents were taken to Baquba, about 40 miles north of here, and shown an array of weapons, including U.S.-made M60 and M48 tanks, mortars, recoilless rifles and other equipment.

A briefing officer, intent on underlining the American manufacture of the Iranian arms, appeared startled when reporters discovered in the stockpile Soviet-built armored personnel carriers and rocket-propelled grenade launchers.

The Army command said Iraqi forces have captured 5,000 tons of weapons, and have destroyed 62 tanks, 35 artillery guns and 39 armored cars.

There was confusion today over last night's air raid in Baghdad, as the civil defense command claimed that a massive antiaircraft barrage was triggered by a helicopter that had wandered off course into air defense radar.

However, the claim did not explain the sound of jet fighters heard by reporters here or the flashes of explosion in northeastern Baghdad.

There was no air raid siren alert before the apparent attack, and the civil defense explanation was interpreted by observers as explaining away the lack of the alert.

News agencies reported from Tehran:

Prime Minister Mohammed Ali Rajai told a Japanese interviewer that "America is in no way concerned" with the 52 American hostages held in Tehran since Nov. 4.

Tehran Radio reported him as telling the television reporter: "Even if all were killed, America would not consider it important, for it uses them as a pretext for any action to advance its interests."

Rajai also said, according to the radio, that Iraq is working in coordination with the United States in the Gulf war.

"Any country seeking to maintain past colonial relations will wage war against us," he added. "We see Saddam's motives in terms of America and the superpowers whose arms are used against our people."