Sporadic fighting broke out in Chechnya's southern mountains and both sides said they had made advances in the eight-month war and had killed several of their opponents.
A Kremlin spokesman said that Sergei Zverev, deputy to the civilian administrator in the region, and Nusreda Khabuseyeva, deputy to the Moscow-appointed mayor of Grozny, were killed when their car ran over a mine in a southern suburb.
Mayor Supyan Makhachayev, who was also in the car, suffered head injuries. Shots were fired from nearby bushes after the car hit the mine.
"We think the terrorist attack was aimed at killing the mayor of Grozny," the spokesman, Konstantin Makeyev, said by telephone. He added that Deputy Prime Minister Nikolai Koshman, Russia's main civilian envoy in Chechnya, had flown to the region to investigate.
The deputy speaker of Russia's lower house of parliament, Vladimir Lukin, said after the mine explosion: "We control Chechnya, it is a part of Russia."
"Territorial integrity is what we ask, no more, no less," he added, during a visit to the Estonian capital Tallinn.
"This is going to be a protracted guerrilla war with defeats and successes for both sides," Yevgeny Volk of the Heritage Foundation think-tank in the U.S. said. "This kind of fighting is not easy to finish off because a new generation of fighters appears every year."
Russia has seen its losses rise in the province, with soldiers increasingly being trapped in hit-and-run rebel attacks. One of the bloodiest was on a column in early March, when 20 servicemen were killed.
But the military has launched a large-scale offensive in the southeastern mountains of Chechnya and officials said they have sealed off about 400 guerrillas.
Russia's news agency quoted an official at the military headquarters in Mozdok as saying: "These are the best-organized extremist units led by the prominent field commanders, including Arab-born field commander Khattab. A large number of mercenaries remain in the Nozhay-Yurt and Vedeno districts."
Moscow has said it will seek and "destroy" Khattab and fellow commander Shamil Basayev, Russia's most wanted men.
The fighters have pledged to pursue a guerrilla war, using the same lightning raids which helped force the Russian army out of the province after the last Chechen war in 1994-96.
But on the rebel Internet Web site, Kavkaz.org, the guerrillas said they had killed four "aggressors" near Zhani-Vedeno, south of the capital, and had continued launching sporadic attacks in Grozny, which Russia took months ago.
"Facts are facts, the Chechen military forces command the initiative and demonstrate the absolute lie of the Kremlin that it is 'in control of Chechnya', Khattab told the Web site.
The rebels said over the weekend they had killed more than 50 Russian troops in "a special operation." Moscow denied such losses but said Chechen rebels had attacked troops outside Grozny, killing three Russians.
Interfax quoted officials as saying Russia lost nine soldiers over the past three days, compared with guerrilla losses which they put at 70. Each side has regularly inflated the other's losses.
"Russian units are carrying out special operations to wipe out guerrilla groups in the Argun Gorge and the Achkhoi-Martan districts," Interfax said.
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