Tokyo stocks plummeted Monday, with the Nikkei index falling over 6% and closing at a four-month low on concern about the adverse economic impact from Friday’s deadly quake and tsunami. The 225-issue Nikkei Stock Average nosedived 633.94 points, or 6.18%, from Friday to 9,620.49. The broader Topix index of all First Section issue on the Tokyo Stock Exchange dropped 68.55 points, or 7.49%, to 846.96.

Almost all 33 sectors on the TSE lost ground, with the insurance sector leading decliners, followed by the oil and coal products and consumer finance sectors. The construction se

Both indexes extended losses registered Friday after the powerful earthquake devastated many cities and towns in northeastern Japan. It also partially paralyzed some functions in the Tokyo metropolitan area, such as public transportation, affecting corporate activity.

‘‘The impact of radiation remains unclear,’’ said Masumi Yamamoto, market analyst at Daiwa Securities Capital Markets Co, adding, ‘‘The effect of the power shortage (triggered by the quake) has been enormous, chilling market sentiment.’‘

The initial quake occurred Friday afternoon shortly before the market closed, triggering panic selling that sent the index around 180 points lower to close at 10,254.43, but that did not allow investors to fully show their reaction to the news at the time.

Tokyo Electric Power Co faced massive sell orders after the earthquake crippled some of its nuclear reactors in Fukushima Prefecture.

A fresh explosion at its nuclear power plant raised concern about the seriousness of the earthquake damage, while the utility firm’s planned power outages also disrupted factory operations and transportation.

Major automakers fell across the board as they were forced to suspend operations at their plants largely due to shortages of supplies, while construction-linked shares surged on investors’ expectations for an increased demand for rebuilding.