The UN Security Council has strongly condemned North Korea's launch of a long-range rocket.
After an urgent meeting in New York, the council said it would soon adopt a new sanctions resolution in response.
Pyongyang said it fired the rocket to place a satellite in orbit but critics believe the real purpose was to test ballistic missile technology.
Sunday's launch came weeks after North Korea conducted a fourth nuclear test. Both acts violate existing sanctions.
Amid the tension, a North Korean patrol boat briefly crossed into South Korean territory near the island of Socheong early on Monday morning, according to South Korea's Defense Ministry.
The ministry said that it retreated back across the border - a boundary line Pyongyang disputes - shortly after South Korean forces fired warning shots into the water around it.
'Serious violation'
Speaking after the closed-door talks, the Security Council said the launch was "a serious violation".
US Ambassador to the UN Samantha Power said Washington would now "ensure that the Security Council imposes serious consequences" on Pyongyang.
"There can be no business as usual," she said, adding that "we'll come up with something tough".
Ms Power's words were echoed by Japanese envoy Motohide Yoshikawa, who said sanctions must be strengthened.
"The existing sanctions have not stopped North Korea from developing nuclear weapons," he said.
The council meeting was requested by South Korea, Japan and the US.
Sunday's launch, which North Korea had said last week it would carry out, was hailed by state media as a "fascinating vapour... trailing in the clear and blue sky in spring of February on the threshold of the Day of the Shining Star".
A statement said a new Earth observation satellite, Kwangmyongsong-4, had successfully been put into orbit less than 10 minutes after lift-off from the Sohae space centre in North Phyongan province.
Hailing it as part of the country's peaceful space programme, a state TV newsreader said the launch had been ordered by North Korea's leader Kim Jong-un and that more launches were planned.
South Korean MPs were told by the country's spy agency later on Sunday that the launch should be treated as a ballistic missile test, as the satellite it put into orbit would be useless.
The MPs were also reportedly told North Korea had the technology for intercontinental ballistic missiles and was preparing a fifth nuclear test.
North Korea last fired a long-range rocket in 2012, putting what it claimed was a communications satellite into orbit. However, experts said that satellite appeared to spin out of control and the revolutionary songs that Pyongyang said it was broadcasting were never detected.
The payload this time was presumed to weigh 200kg (440lbs), double the size of the 2012 launch, but still much lighter than the 800-1,500kg usual for a satellite.
February 2016: Launch of rocket reportedly carrying satellite
May 2015: North Korea announces it has successfully tested a submarine-launched missile for the first time, but scepticism is then poured on the claim
Dec 2012: North Korea launches three-stage rocket, says it successfully put a satellite into orbit; US defence officials confirm object in orbit
Apr 2012: Three-stage rocket explodes just after take-off, falls into sea
Apr 2009: Three-stage rocket launched; North Korea says it was a success, US says it failed and fell into the sea
Jul 2006: North Korea test-fires a long-range Taepodong-2 missile; US said it failed shortly after take-off
