MAKHACHKALA, Russia — At least 25 gunmen crossed from Chechnya into the neighbouring Russian region of Dagestan on Monday, killing at least three border guards and seizing dozens of hostages at a school in a remote mountain village, a police official said.

The gunmen attacked a border guard unit on the internal frontier between Chechnya and Dagestan, killing at least three servicemen and wounding 10 others before entering the village of Shauri, where they seized up to 40 hostages at a school, said Roman Shchekochikhin, a spokesman for the Interior Ministry in southern Russia.

However, a Dagestani emergency official later said the attackers had left Shauri, taking three hostages with them. They were headed back toward Chechnya, said Yusup Koichukayev, a duty officer with the Ministry of Emergency Situations in Dagestan.

The ITAR-Tass news agency quoted a spokesman for the Russian military in Chechnya, Vasily Panchenkov, as saying the attackers took three hostages in Shauri.

Muslim Tsupmilov, a spokesman for the Federal Security Service's border guards agency in Dagestan, said nine servicemen were killed in fighting with the gunmen.

Interior Ministry and border troops were headed to the area, but it is remote and hard to reach, Shchekochikhin said. Tsupmilov said a top border guard official and Dagestani Deputy Interior Minister Magomed Omarov left the regional capital, Makhachkala, for the Tsunti district, where Shauri is located.

The current war in Chechnya began in 1999 after Chechen rebels carried out attacks in villages in western Dagestan and after the Kremlin blamed militants for apartment-building bombings that killed some 300 people in Moscow and other Russian cities.