New Delhi, Oct 5(DC): Prime Minister Narendra Modi and Russian President Vladimir Putin have reportedly signed a deal for five Russian S-400 Triumf missile shield systems, one of the world's most lethal surface-to-air missiles.

The long-range missile systems will bolster India’s air-defence capabilities along the 4,000-km-long India-China border.

S-400 is known as Russia's most advanced long-range surface-to-air missile defence system. China was the first foreign buyer to seal a government-to-government deal with Russia in 2014 to procure the lethal missile system and Moscow has already started delivery of an undisclosed number of the S-400 missile systems to Beijing.

The S-400 is an upgraded version of the S-300 systems. The missile system, manufactured by Almaz-Antey, has been in service in Russia since 2007.

The deal was signed between Prime Minister Narendra Modi and Russian President Vladimir Putin on Friday afternoon amid a threat of tough sanctions from the US.

The US has hinted at tough sanctions against any nation that buys advanced military hardware from Russia. Russia has been an important supplier of defence hardware to India for decades.

According to reports, deal for space cooperation has been inked between Russia and India.

There will be an Indian monitoring station built near the Russian city of Novosibirsk in Siberia.

The bilateral talks between the two leaders are going on.

Vladmir Putin is India on a two-day India visit. He arrived in New Delhi on Thursday.