In this story:

• Dispute over diplomats
• Exercises will include missiles
• Related stories and sites

TEHRAN, Iran (CNN) -- Iran began military exercises near its border with Afghanistan on Tuesday, which could ratchet up the tensions between the two countries.

About 70,000 Iranian soldiers were in Torbat-e Jam in northeastern Khorasan province for the three days of exercises -- the first maneuvers near the border since Iran's 1979 Islamic revolution.

Afghanistan warned Iran on Monday against increasing tension on the border, saying the exercises constitute threatening behavior. The two countries are in the midst of a dispute over Iranians held by Afghanistan's militant ruling militia, the Taliban.

Iran has denied any attempt to threaten its neighbor but says the maneuvers are intended to test new weapons and strengthen Iran's defense capabilities.

"The Iranian nation ... is peaceful and seeks peace and security for humanity and does not intend to commit aggression against any country," Iranian state television quoted the Islamic Revolutionary Guard Corps commander, Maj. Gen. Yahya Rahim Safavi, as saying to troops before parades kicking off the maneuvers.

Safavi, however, also said that Iran would not tolerate foreign interference at its borders "and will defend its territorial integrity."

Hossein Salami, a military official at the war games' headquarters, quoted by the official news agency IRNA, said, "Contrary to remarks by international circles, these maneuvers do not aim at any probable confrontation with or aggression against Afghanistan."

Tensions between the two countries have increased since Iran accused the Taliban, which controls most of Afghanistan, of detaining 11 Iranian diplomats, one journalist and 35 truck drivers.

The Taliban has said it knows nothing about the diplomats. It admits to holding about 30 Iranians but alleges they were arming its opponents. The diplomats disappeared after the Taliban captured the northern Afghan city of Mazar-e-Sharif from opposition forces.

The Taliban's top leader has said the diplomats were "probably dead." On Tuesday, Iran said it would ask the United Nations to investigate the fate of the missing diplomats. The Taliban asked the world body on Monday to mediate the dispute between the two countries.

Iran is suspected of backing the northern-based opposition to the Taliban, and Pakistan is widely believed to provide arms and other support to the Taliban. The Taliban reported Tuesday that it had captured 30 villages in a fresh offensive against the opposition in the center of the country.

Shiite Muslim Iran has accused the mostly Sunni Muslim Taliban of giving Islam a bad name and has criticized the Taliban's severe restrictions on women.

Iran also has refused to recognize the Taliban as Afghanistan's government and considers ousted President Burhanuddin Rabbani as Afghanistan's legitimate leader.

State-run television also quoted Safavi as saying medium-range Sam-6 missiles would be used during the exercises. The broadcast was monitored by the BBC in London.

The actual military maneuvers, which begin Wednesday, involve ground and air troops from the Revolutionary Guard and the volunteer Basij Resistance Forces. The exercises are named "Ashura 3" for the holiday marking the martyrdom of Shiite Islam's most revered figure, Hussein, the grandson of Prophet Mohammed.

State television showed helicopters and transport planes flying over long lines of tanks, self-propelled guns and armored vehicles decked with Iranian flags.

Iranian media earlier said 160 tanks, 60 cannons and an unspecified number of aircraft and helicopters would be used in the exercises, which cover 600 square kilometers (230 square miles).

Revolutionary Guards were deployed on the border with Afghanistan last week to monitor the civil war there, and former President Hashemi Rafsanjani said Iran might resort to force to free the Iranians.

In the past few years, Iran has beefed up its defenses along the border with Afghanistan, a key transit route for opium and heroin headed to Europe from Afghanistan and Pakistan -- the so-called "Golden Crescent."

The Associated Press and Reuters contributed to this report.