Undated (AP) _ Iraq claimed its warplanes demolished an ''important Iranian army camp'' today, while Iran announced it had installed a surface-to-air missile defense system around Tehran and hit a raiding Iraqi plane over the city.

An Iraqi military spokesman said in Baghdad that Iran's Hamid Camp was attacked three times in eight minutes beginning at 8 a.m. by a total of 22 warplanes in a new escalation of the two Persian Gulf countries' four-year-old war.

''Our aircraft totally demolished this important enemy camp and returned safely to base,'' said the spokesman, on condition he not be identified. He did not disclose the location of the camp.

Less than 24 hours earlier, Iraq claimed its warplanes demolished the Iranian army camp of Khaneh in southern Iran.

Iran's official news agency, the Islamic Republic News Agency, said air force commander Col. Hushang Seddiq reported completion of a surface-to-air missile defense grid around the Iranian capital city of Tehran.

The agency, monitored in Nicosia, Cyprus, quoted Seddiq as saying one of the SAM missiles hit an Iraqi jet over Tehran Monday night.

IRNA did not say whether the plane crashed. Iraq said all its raiding jets returned safely to their bases.

IRNA also did not disclose the type of surface-to-air missile being used or its source.

Both Iran and Iraq reported the 8:45 p.m. air raid on Tehran, the second on the city in 24 hours and the 36th since the two countries began attacking each others' cities last March.

IRNA said six people were injured and two empty houses were damaged by the raid. Tehran was blacked out for 20 minutes as intense anti-aircraft fire crackled over the city, the news agency said.

The agency said Iraqi jets also bombed Piranshahr and Gilan-e-gharb in Kurdistan province Monday, causing ''some damage'' in the two cities.

The border towns of Paveh and Bakhtaran in the central sector of the front, and Abadan and Khorramashahr on the Shatt Al-Arab waterway also were damaged by Iraqi artillery shelling in the past 24 hours, IRNA said.

Iran retaliated by bombing the Iraqi towns of Diyana and Shaqlawa from the air, and shelling economic and military installations along a 480-mile stretch of the battlefront, causing ''heavy damage'' IRNA said.