NEW YORK - Tighter security checks, bomb-sniffing dogs and traffic delays greet locals and visitors in New York this week, as the city hosts world leaders and foreign delegations to the United Nations General Assembly, just days after a bombing in a bustling Manhattan neighbourhood.

The New York Police Department has deployed an additional 1,000 officers and state troopers and implemented tighter security checks at subway stations. Mayor Bill De Blasio has said the police presence this week will be "bigger than ever".

Security in the city was substantially stepped up after the country was shaken by three weekend attacks.

A bomb in a dumpster in Chelsea district, Manhattan, exploded on Saturday local time (Sunday Sept 18, Singapore time), injuring 29 people. Another bomb that failed to detonate was found nearby. In New Jersey, a pipe bomb went off along the route of a charity road race but no injury was reported, and a stabbing attack at a Minnesota shopping mall wounded nine.

The weekend attacks have thrust security fears into the heart of the US presidential election, but on the ground, life in Manhattan appeared to be back to normal by Monday local time.

The area around the scene of the blast was as busy as ever. Even though the police had blocked off the road, many passers-by stopped to take photographs of the scene, while others barely gave the scene a second look. By night time, the road was opened to foot traffic.

Many signs of damage from the explosion were evident even though the remnants of the bomb and the dumpster had been removed. Windows of nearby buildings were taped up or completely blown out.

An SUV vehicle parked near the site seemed to bear the brunt of the damage with a cracked windshield, while a gym had cracks on its large front windows. It was one of the few businesses that remained closed in the area after the blast.

Workers were seen clearing up glass and debris at the scene while it was back to business at a supermarket along 23rd Street, less than 100m from the blast site. A steady stream of customers were buying their groceries on Monday night. The subway station on 23rd Street was also functioning as normal.

Traffic was slower than normal in some places due to UN security zones. The New York City Transit had already warned commuters before the weekend blast that there may be severe delays on bus lines in and out of Manhattan.