MOSCOW: Russian Prime Minister Vladimir Putin on Monday made an unannounced visit to Chechnya, the government said, amid concerns over mounting Islamist violence in Russia's restive Caucasus region.

The Russian strongman "visited Chechnya on a short working visit" for talks with its leader Ramzan Kadyrov on the region's social-economic situation and problems of employment, a government spokesman told AFP.

Visits by Russian leaders to Chechnya are rare events and Putin's surprise trip came after a series of bloody attacks in the Russian Caucasus.

The visit was shrouded in secrecy and even top Chechen officials appeared unaware of the prime minister's trip. "I do not have such information," Kadyrov's spokesman told AFP.

The Russian government spokesman said Putin had already returned to Moscow.

Pictures broadcast on Russian television showed Putin, dressed in a white sports jacket and surrounded by heavily armed guards, clambering out of a military helicopter in Chechnya with Kadyrov and striding through a field.

He then laid a wreath at the grave of Kadyrov's father and ex-president of Chechnya, Akhmad Kadyrov, who was assassinated in a bomb attack in 2004.

"He did not live for nothing and he did not give his life for nothing," Putin said at the graveside as his son stood by holding a copy of the Koran.

"He set the basis for peace in Chechnya. We will always remember him," said Putin.

On Friday, a double suicide bombing killed four police in the Chechen capital Grozny in an attack which Ramzan Kadyrov said could have been aimed at killing him at a ceremony to mark his birthday.

Last week over 20 people were killed in a bomb attack on the police headquarters in Nazran, the main city of the region of Ingushetia which neighbours Chechnya.

There has been alarm in Moscow over the regularity of attacks on security forces in the overwhelmingly Muslim regions of Russia's Caucasus, where the pro-Kremlin local authorities are battling Islamist insurgents.

But Europe and the United States have also been shocked over attacks on human rights activists, including the murder in July of Natalya Estemirova who headed the Grozny office of top rights group Memorial.

Earlier this month, the head of a local childrens' organisation Zarema Sadulayeva and her husband Alik Dzhabrailov were found shot dead with their bodies stuffed into a car boot.

Chechnya was the site of two separatist wars between Chechen rebels and the Russian central government after the collapse of the Soviet Union in 1991.

Kadyrov is a hugely controversial figure, praised by the Kremlin for restoring some stability to Chechnya but hated by rights activists, who accuse him of letting a personal militia carry out kidnappings and torture.

In April, Russia ended its controversial "anti-terror operation" in Chechnya, a move that analysts said gave the maverick leader a freer hand in running his war-ravaged region.