Donald Trump has won presidential primaries in all five north-eastern US states voting while Hillary Clinton took four, US media say.
Mr Trump looks set to cement his lead in the Republican race with victories in Connecticut, Delaware, Maryland, Pennsylvania and Rhode Island.
For the Democrats, Mrs Clinton was denied a clean sweep by Bernie Sanders who won in Rhode Island.
Mr Trump’s rivals have already shifted their attention to upcoming states.
Ted Cruz and John Kasich have teamed up to help each other in the Indiana, Oregon and New Mexico primaries.
Mr Trump has condemned their pact as a sign of weakness and desperation.
Story of the night so far
- Trump wins five states – Pennsylvania, Connecticut, Maryland, Rhode Island, Delaware
- Clinton wins three states – Maryland, Delaware, Pennsylvania, Connecticut
- Sanders wins one state – Rhode Island
Speaking in New York after Tuesday’s results came in, Mr Trump said his rivals’ plan was another example of the Republican establishment conspiring against him.
“I think it’s a good thing because it shows weakness, it shows ineffectiveness, but really it’s collusion,” he said. “The Republican party needs something much better than that.”
Mr Trump is edging closer to securing 1,237 delegates, which would mean he could avoid a contested convention this July in Cleveland. A contested convention would see party delegates – Republican officials and activists – choose the nominee.
Analysis: Anthony Zurcher, BBC North America reporter
There’s winning, and then there’s WINNING.
Donald Trump’s night is shaping up to be the latter, as he steamrolls his opposition in all five of mid-Atlantic states voting on Tuesday.
This campaign season has been punctuated with a series of theories about how and why Mr Trump’s presidential ambitions would eventually be thwarted. The latest was that he’d never be able to win more than 50% of the vote as the field narrows. It appears likely that he’ll easily surpass that mark across the board and claim the lion’s share of the delegates at stake.
During a primary night speech that took place before the polls even closed, Texas Senator Ted Cruz promised that his campaign was now heading to “more favourable terrain”. He’s setting up a firewall in Indiana, but there’s a Trump-fuelled conflagration heading his way.
The New Yorker still has work to do to clinch the Republican nomination, but after his latest performance such a prospect seems increasingly likely.
Speaking at Philadelphia Convention Center after her latest wins were announced, Mrs Clinton said her campaign was setting “bold, progressive goals” to improve lives in the US as “both dreamers and doers”.
“We believe in the goodness of our people and the greatness of our nation,” she said.
Speaking in Huntington, West Virginia, after the vote, Mr Sanders vowed to fight to the end of the nomination process, saying he would attract broad support in November’s election.
“The reason that we are generating this enthusiasm is because we are doing something very unusual in contemporary politics. We are telling the truth,” he said.
Despite some success, it is unlikely Mr Sanders will be able to overcome Mrs Clinton’s lead to become the Democratic nominee for president.
Meanwhile the hope of a contested convention is keeping Mr Kasich and Mr Cruz in the race. Both candidates have no chance of securing the nomination outright.
Read more on the US election:
Can the Cruz-Kasich tag-team beat Trump?
Can Trump really change his image?
Mr Kasich is to give Mr Cruz a “clear path” by not campaigning in Indiana and Mr Cruz will reciprocate in New Mexico and Oregon. But neither has endorsed tactical voting among their supporters.
Speaking in Indiana on Tuesday night, Mr Cruz said his supporters could look forward to some success as the race moved on.
His event was held at a basketball court where some scenes were filmed for the 1986 film Hoosiers, about a small-town high school basketball team that wins the state championship.
The Texas senator attempted to recreate a scene from the film but was mocked on social media for referring to a basketball “ring” rather than a “hoop”.