Uber and Lyft, two of the hottest startups, are running head-to-head in the new market of on-demand transportation. Competition between the two app-driven ride request services was already fierce, but now they each claim the other is resorting to dirty tricks to sabotage business.

Lyft claimed on Monday that Uber employees have ordered and then cancelled thousands of Lyft rides since October, slowing its service and causing lost fares. Uber called the claims “patently false” and then on Tuesday accused Lyft of doing exactly the same thing. Both claim that the other is causing financial hardships that are preventing projected growth.

“A number of Lyft investors have recently been pushing Uber to acquire Lyft,” the Uber spokeswoman claimed. “One of their largest shareholders recently warned that Lyft would ‘go nuclear’ if we do not acquire them. We can only assume that the recent Lyft attacks are part of that strategy.”

Lyft denied those claims and said Uber was being deceitful. “Lyft is approaching IPO-level revenue,” a representative said.

While both companies have drawn scrutiny from regulators over insurance and road safety issues, after some initial regulatory challenges Lyft launched in New York City late last month. The move drew criticism for taking away traditional taxi driver business without being properly regulated. Lyft’s presence is limited to the U.S., but its popularity is growing as it enters more cities. Uber, which began life as a premium black town-car service, operates in more than 40 countries and many U.S. cities.

The accusations come as Uber and Lyft offer new services that increasingly mimic each other’s. Both let people request rides from their smartphones with a credit card on file. Lyft was a cheaper alternative to taxis used for hailing rides from private cars. But Uber now offers its own, less expensive service too, called UberX. And last week, both announced new carpooling services that let riders share with each other and split the cost.