The show of force comes a month after North Korea's deadly shelling of a front line island.
The drills, taking place at training grounds in mountainous Pocheon near the Koreas' heavily fortified border, signalled South Korea's determination to demonstrate its military strength at the risk of further escalation with North Korea.
Vulcan artillery vehicles fired into a wide valley with numbers carved on to hills below as the army and air force launched the drills about 20 miles from the North Korean border.
They are the armed forces' largest joint firing exercises this year, and the biggest-ever wintertime air and ground firing exercises, government and army officials said on condition of anonymity, citing department rules.
Exactly one month ago, routine South Korean live-fire drills from Yeonpyeong Island in the Yellow Sea triggered a shower of North Korean artillery that killed two marines and two construction workers. It was the first military attack on a civilian area since the 1950-53 Korean War ended in a truce.
Medvedev hails nuclear treaty
RUSSIAN president Dmitry Medvedev has welcomed the US Senate's decision to ratify a landmark US-Russian nuclear arms control treaty and voiced hope that Russian legislators will follow suit.
The Russian parliament is scheduled to have its next session tomorrow.
Sedition probe over website
Malaysian police may charge a man with sedition for allegedly creating a Facebook page that mocked the country's former king.
The suspect is believed to have set up the page to criticise Sultan Iskandar Ismail, a state ruler who was Malaysia's king for five years in the 1980s, a police official said. Sultan Iskandar died at the age of 77 last January.
The 40-year-old is being investigated for sedition, which is punishable by three years in prison.
Videla jailed for life for killings
Former Argentine dictator Jorge Videla has been sentenced to life in prison for the torture and murder of 31 prisoners in 1976.
Videla, 85, who led the military coup that installed Argentina's 1976-1983 dictatorship, was considered the architect of a dirty war that killed 13,000 people.
Suicide attack kills policeman
A SUICIDE bomber struck at a police checkpoint in northern Afghanistan today, killing one officer.
The attacker detonated his explosives as he was stopped at a checkpoint in the Kunduz. Three civilians were also wounded.
It is the second attack in less than a week in Kunduz.
Greece: The Socialist government has won a key budget vote calling for deeper austerity measures in the crisis-hit country and promising to avoid default despite a soaring national debt. The package includes higher taxes and cuts in health and defence spending.
Japan: Emperor Akihito celebrated his 77th birthday today and urged the people of Japan to pay heed to the needs of the country's growing number of elderly people.