NICOSIA, Cyprus (AP) _ Iran launched a missile attack today on Kirkuk, Iraq's northern oil capital, and said 75 people have been killed and more than 100 wounded in new Iraqi chemical bomb attacks on Kurdish villages.

Iran's official Islamic Republic News Agency said Iraqi warplanes dropped bombs containing mustard and nerve gases in the Qara Dagh region of northeastern Iraq during the six days that ended Saturday.

It quoted Iranian-backed Kurdish guerrilla sources as saying the villages of Susiyan, Doukan, Balakha, Jafaran and Oliyan were hit.

There was no independent confirmation and no comment by Baghdad, which has been fighting a brutal mountain war against the Kurdish guerrillas, who seek an independent homeland.

Qara Dagh is 15 miles west of the front in a two-week-old Iranian offensive into the Kurdistan mountains, where Iran claims Iraqi warplanes dropped cyanide and mustard gas bombs March 16-17 on three Kurdish towns ''liberated'' in the push. Iran claims 5,000 civilians were killed and 5,000 injured.

Western correspondents who visited one of the towns, Halabja, last week reported seeing hundreds of bodies unmarked by bullet or shrapnel wounds. Hundreds more Iraqi Kurds with severe burns and respiratory ailments consistent with exposure to poison gas have been seen in Tehran hospitals.

IRNA claimed Thursday that Iraqi warplanes also dropped chemical bombs on Marivan in northwestern Iran, killing ''a number'' of civilians.

Meanwhile, Iranian Revolutionary Guards were reported advancing westward through Kurdistan and said they bottled up 5,000 Iraqis around a hydroelectric dam on Lake Darbandikhan, 80 miles east of Iraq's big Kirkuk oilfields.

The Iranian missile strike on Kirkuk was announced after Iraq declared it would halt its missile attacks on Iranian cities for three days beginning today as Prime Minister Turgut Ozal of Turkey visits Baghdad.

IRNA said two missiles were fired at a ''military target'' in Kirkuk city early today ''in retaliation for Iraqi missile attacks on Iran's residential areas.''

The official Iraqi News Agency, also monitored in Nicosia, only reported one missile hitting Kirkuk, saying it exploded in a residential district, killing or wounding ''many civilians, including women and children.''

The missile struck only a half-hour after the time Iraqi said it would stop missile attacks. Ozal was to arrive in Baghdad this afternoon.

Iraq sent three long-range missiles Thursday into the holy city of Qom 100 miles south of Tehran and the central city of Isfahan.

There was no official response from Tehran when Iraq announced Thursday that it would halt its missile attacks at midnight Baghdad time. But an Iranian embassy spokesman in Ankara, Turkey's capital, said Thursday that his country's attacks on Iraqi cities would ''automatically come to an end'' if the Iraqis stopped their air and missile strikes.

Both sides have fired more than 250 missiles into each other's cities since Feb. 29, killing hundreds of civilians.

On that day that the ''war of the cities'' flared anew, Ozal was visiting Tehran and several missiles exploded near the downtown hotel where his delegation was staying.

Iraq said the latest truce would last until Ozal's Baghdad visit ends. Officials in Ankara said he would fly home Sunday.

Turkey maintains good relations with both belligerents and has in the past tried to mediate an end to their 7-year-old war.

Associated Press photographer Greg English reported from Kurdistan that Iran's Revolutionary Guards were pushing westward in the offensive launched March 16.

English, among a group of Western correspondents flown to the battle zone Thursday, reported from the Kurdish town of Dojaila that artillery rumbled to the west and it was clear ''the Iranians have made significant gains.''

The Iranians claim their forces occupy the eastern and southern shores of Lake Darbandikhan and hills overlooking the strategic dam and power station on the lake's southern tip, where they say they have surrounded 5,000 Iraqis who apparently still hold the dam.