Prime Minister Robert Mugabe's government today seized companies owned by the party of Joshua Nkomo and police raided its headquarters in moves that appear to be leading toward the breakup of the coalition between the two former guerrilla allies.

Nkomo said as much at a press conference this evening in a bitter reference to Mugabe's Zimbabwe African National Union party.

"This is the ZANU way of doing things," he said. "They worked with us up to a point. Now they think they can dispense with us, just like that. It would be better to shake hands and go our separate ways."

"The slap Mugabe has given me in my face is very hard," Nkomo said, but it was up to the prime minister to dismiss his party from the coalition Cabinet. He made it clear he has no intention of quitting at this point. ZANU has 57 of the 100 seats in parliament and could rule alone.

A break in the coalition formed two years ago when this key southern African nation won independence after a bloody war could lead to sharp divisions along tribal lines. Mugabe is from the majority Shona tribe while Nkomo is leader of the Ndebele minority centered in the southwest.

Today's police raid and takeover of the companies involved in agriculture, investment and commerce were Mugabe's first concrete actions against Nkomo's Patriotic Front party after 10 days of threats following the discovery of huge arms caches on farms owned by the junior coalition partner.

Arms discoveries continue to be announced almost daily despite a denial by the Patriotic Front of any advance knowledge of the caches.

Mugabe said last weekend that the caches include "mortars, bazookas, recoilless rifles, submachine guns, heavy machine guns and antiaircraft weaponry."

There is estimated to be enough weaponry to outfit 3,000 to 5,000 troops and, in addition, more than 40 military trucks, radios and jamming devices. Battlefied medical supplies also have been found.

Mugabe accused Nkomo of trying to overthrow the government and launched an unprecedented personal attack on the veteran nationalist, saying that to have Nkomo in the government was like having "a cobra in a house."

"The only way to deal effectively with a snake is to strike and destroy its head," Mugabe said, in a reference that has been interpreted to mean that getting rid of Nkomo will be the end of his party and will allow the prime minister to proceed with plans to form a one-party state.

Mugabe also criticized Nkomo's role during his three decades in the liberation struggle. Nkomo responded today by calling such remarks "childish" and added, "Where was Mugabe when we started?" Both men were imprisoned for 10 years under the white-minority rule of former prime minister Ian Smith.

Nkomo defended the arms caches saying, "All of us know that a lot of arms have been buried all over the country," as a result of the war. "We must not pretend," he added.

He also denied any plot "to overthrow the government in which we serve."

Home Affairs Minister Richard Hove said the companies were seized because they were "likely to endanger, disturb or interfere with defense, public safety or public order." The action was carried out under a 1971 law implemented by the Smith government.

Nkomo said many of the companies, worth "millions of dollars," that were seized were engaged in cooperative farming and successfully demonstrating a future path of development for the country.

"Now it is snatched away. The whole program is destroyed," he said.

Nkomo also complained that his personal farm at Kezi in southwestern Zimbabwe had been sealed off by police. He said he feared for the health of his 54-year-old wife who recently had a major operation and is not allowed to leave the farm.

Three policemen blocked the entry of the Patriotic Front's headquarters in downtown Salisbury. A party official said about 15 policemen were searching everything and had taken away some documents.

Today's anti-Nkomo actions were carried out while he and Mugabe were at a four-hour Cabinet meeting. No information was available on the meeting, but Nkomo said the atmosphere was "hot."

Nkomo said he attended the meeting, despite Mugabe's hostility, "for the sake of the country."

The central committee of ZANU was meeting tonight to discuss the political situation. Mugabe said last weekend that a decision on the role of Nkomo's party in the government would be announced this week.